Chinook Salmon (Oncorhynchus tshawytscha): COSEWIC assessment and status report 2020

Official title: COSEWIC assessment and status report on the Chinook Salmon Oncorhynchus tshawytscha, Designatable Units in Southern British Columbia (Part Two - Designatable Units with High Levels of Artificial Releases in the Last 12 Years), in Canada

Committee on the Status of Endangered Wildlife in Canada (COSEWIC)
Designatable Unit 1: Southern Mainland Boundary Bay, Ocean, Fall population - Threatened 2020
Designatable Unit 6: Lower Fraser, Ocean, Summer population - Endangered 2020
Designatable Unit 13: South Thompson, Stream, Summer 1.3 population - Endangered 2020
Designatable Unit 15: Lower Thompson, Stream, Spring population - Endangered 2020
Designatable Unit 18: South Coast - Georgia Strait, Ocean, Fall population - Data deficient 2020
Designatable Unit 20: East Vancouver Island, Ocean, Summer population - Endangered 2020
Designatable Unit 21: East Vancouver Island, Ocean, Fall population - Special concern 2020
Designatable Unit 22: South Coast - Southern Fjords, Ocean, Fall population - Data deficient 2020
Designatable Unit 23: East Vancouver Island, Ocean, Fall (EVI + SFj) population - Not at risk 2020
Designatable Unit 24: West Vancouver Island, Ocean, Fall (South) population - Threatened 2020
Designatable Unit 25: West Vancouver Island, Ocean, Fall (Nootka and Kyuquot) population - Threatened 2020
Designatable Unit 26: West Vancouver Island, Ocean, Fall (WVI + WQCI) population - Data deficient 2020

COSEWIC Assessment summary

Assessment summary - November 2020 - Chinook Salmon - designatable unit 1

Common name

Chinook Salmon - Designatable Unit 1: Southern Mainland Boundary Bay, Ocean, Fall population

Scientific name

Oncorhynchus tshawytscha

Status

Threatened

Reason for designation

Mature fish in this population spawn in tributaries to Boundary Bay such as the Serpentine, Nicomekl and Little Campbell rivers, in southern British Columbia. This wildlife species occurs in highly altered freshwater and marine habitats. Ongoing low marine survival, bycatch, and fish culture effects are cumulative threats to the remaining wild fish. Hatchery releases are ongoing and have included fish from other populations, threatening the genetic integrity of the few remaining wild fish. While hatchery production has allowed the total population size to increase, a consensus of expert opinion estimates fewer than 1000 mature wild fish remain.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Threatened in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 6

Common name

Chinook Salmon - Designatable Unit 6: Lower Fraser, Ocean, Summer population

Scientific name

Oncorhynchus tshawytscha

Status

Endangered

Reason for designation

Mature fish in this population return in summer and spawn at a single site (Maria Slough), in the lower Fraser River. A continuing decline in spawner abundance is expected as a result of highly modified freshwater and marine habitats, low marine survival and harvest. Failed water control structures and low water levels prevented spawners from accessing the spawning site in 2018. A continuing decline in water quality and quantity is expected due to increasing urbanization and runoff.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Endangered in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 13

Common name

Chinook Salmon - Designatable Unit 13: South Thompson, Stream, Summer 1.3 population

Scientific name

Oncorhynchus tshawytscha

Status

Endangered

Reason for designation

Mature fish in this population migrate up the Fraser River in summer, through the Thompson River to spawn in major Shuswap Lake tributaries such as the Seymour, Eagle, Scotch and the Salmon rivers. The estimated number of remaining wild spawners is fewer than 2500 fish, and there is a projected continuing decline in numbers. Threats include decreased water levels (water withdrawal and changes in volume as a result of low marine survival, harvest, and timing of snow melt), agricultural runoff, pollution from transportation accidents, and highly modified freshwater habitats. Such threats are accentuated due to a relatively long freshwater residence.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Endangered in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 15

Common name

Chinook Salmon - Designatable Unit 15: Lower Thompson, Stream, Spring population

Scientific name

Oncorhynchus tshawytscha

Status

Endangered

Reason for designation

Mature fish in this population migrate up the Fraser River in spring to the Thompson River and then into the Nicola, Deadman and Bonaparte rivers to spawn. Marine survival has been low since 2000. There has been a steep decline in the number of mature individuals from 2013 to 2018. This wildlife species faces a number of continuing and severe threats in its freshwater and marine habitat, including post Pine Beetle deforestation, short and long-term effects from wildfires (the large Elephant Hill fire occurred here in 2018), habitat destabilization, and climate-change induced disruption to water quality. Agriculture water withdrawal is substantial and ongoing.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Endangered in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 18

Common name

Chinook Salmon - Designatable Unit 18: South Coast - Georgia Strait, Ocean, Fall population

Scientific name

Oncorhynchus tshawytscha

Status

Data Deficient

Reason for designation

Mature fish in this population return in the fall to rivers flowing into the south coast inlets of the Salish Sea between Burrard Inlet near Vancouver and Toba Inlet to the north. Abundance trend information is available for only two of 19 sites within the range of this relatively remote and poorly documented wildlife species. While these show a stable trend from 2005 to 2018, spawning is thought to occur elsewhere in the northern area. Data are too few to determine status.

Occurrence

British Columbia, Pacific Ocean

Status history

Species considered in November 2020 and placed in the Data Deficient category.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 20

Common name

Chinook Salmon - Designatable Unit 20: East Vancouver Island, Ocean, Summer population

Scientific name

Oncorhynchus tshawytscha

Status

Endangered

Reason for designation

Mature fish in this population return in summer to spawn in the upper reaches of rivers draining the east side of Vancouver Island, from the Koksilah River in the south to the Puntledge River in the north. According to a consensus of expert opinion, fewer than 1000 wild spawners remain in this population. Exploitation rates are relatively high (about 40%), and marine survival estimates have been low for many years. Additional threats include ecosystem modifications (dam construction and channelization) and drought. The contribution of fish from hatcheries confounds the determination of population trends; hatchery-origin spawners may be a continued threat through direct competition and gene flow.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Endangered in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 21

Common name

Chinook Salmon - Designatable Unit 21: East Vancouver Island, Ocean, Fall population

Scientific name

Oncorhynchus tshawytscha

Status

Special Concern

Reason for designation

Mature fish in this population return in fall to the east side of Vancouver Island to spawn in multiple rivers from the Goldstream near Victoria north to Campbell River. Five of the six watersheds within the range of this wildlife species are mostly inhabited by hatchery-origin fish. While the overall abundance in the single remaining watershed is increasing, several large-scale hatcheries aim to augment production within the other watersheds and straying could pose threats from competition and gene flow to the remaining wild fish. Other threats include low marine survival, relatively high exploitation rates, ecosystem modifications and water management/use. This wildlife species could become Threatened if these factors are not properly managed.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Special Concern in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 22

Common name

Chinook Salmon - Designatable Unit 22: South Coast - Southern Fjords, Ocean, Fall population

Scientific name

Oncorhynchus tshawytscha

Status

Data Deficient

Reason for designation

Mature fish in this population return in the fall to the fjords of the Phillips Arm and Bute Inlet near Johnstone Strait in southern BC. Spawners migrate to the remote habitats of the Phillips, Franklin, Orford, and other rivers. While some survey information exists, coverage is incomplete and changes in methodology make it difficult to interpret trends in abundance or recent numbers of mature individuals. Data are too few to assess status.

Occurrence

British Columbia, Pacific Ocean

Status history

Species considered in November 2020 and placed in the Data Deficient category.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 23

Common name

Chinook Salmon - Designatable Unit 23: East Vancouver Island, Ocean, Fall (EVI + SFj) population

Scientific name

Oncorhynchus tshawytscha

Status

Not at Risk

Reason for designation

Mature fish in this population return in fall to spawn in rivers which drain the eastern slope of Vancouver Island’s coastal mountain ridge, such as the Adam, Quinsam, Nimpkish, Salmon and Campbell Rivers. While the population faces a number of threats including competition and gene flow from hatchery production, indices of abundance suggest increasing numbers.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Not at Risk in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 24

Common name

Chinook Salmon - Designatable Unit 24: West Vancouver Island, Ocean, Fall (South) population

Scientific name

Oncorhynchus tshawytscha

Status

Threatened

Reason for designation

Mature fish in this population return in fall to spawn at a large number of sites in rivers along the south west coast of Vancouver Island including the Nahmint, San Juan, Somass-Sproat, Nitinat, and Sarita Rivers. Survey information is available for many spawning locations, and while the overall trends are unclear, <10,000 wild adults are thought to remain. Large-scale hatcheries operating with the aim of augmenting production have resulted in straying of hatchery-origin spawners throughout the range. Such straying likely compromises the genetic composition of spawners and therefore represents a continuing threat to the wildlife species. Other threats include ecosystem modifications (primarily due to slides and sedimentation from forestry) and aquaculture of Atlantic Salmon, all of which are inferred to result in a future decline in numbers of wild fish.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Threatened in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 25

Common name

Chinook Salmon - Designatable Unit 25: West Vancouver Island, Ocean, Fall (Nootka and Kyuquot) population

Scientific name

Oncorhynchus tshawytscha

Status

Threatened

Reason for designation

Mature fish in this population return in fall to the remote Nootka and Kyuquot Sounds on the west coast of Vancouver Island. They spawn in larger rivers such as the Conuma, Gold, Tahsish, and Zeballos Rivers. While this wildlife species spawns at a large number of sites, with survey information being available from many spawning areas, population trends are most likely heavily influenced by hatchery releases aimed to augment natural production. Straying of hatchery-origin spawners has been documented throughout the range and is expected to continue, likely compromising the genetic composition of wild spawners. Other threats include long-term effects from forestry, mainly slides and sedimentation.

Occurrence

British Columbia, Pacific Ocean

Status history

Designated Threatened in November 2020.

Assessment summary - November 2020 - Chinook Salmon - designatable unit 26

Common name

Chinook Salmon - Designatable Unit 26: West Vancouver Island, Ocean, Fall (WVI + WQCI) population

Scientific name

Oncorhynchus tshawytscha

Status

Data Deficient

Reason for designation

Mature fish in this population return in fall to the remote watersheds on the west coast of Vancouver Island, north of the Brooks Peninsula. Adults return to spawn at a number of larger rivers, such as the Goodspeed, Marble, and Klaskish Rivers. Juvenile smolt enter Quatsino Sound after a brief residency in fresh water. While this wildlife species is known to spawn at a number of sites, survey information is available from only one site. This single monitoring site is heavily enhanced by hatchery releases and likely does not represent the entire population. Data are too few to assess status.

Occurrence

British Columbia, Pacific Ocean

Status history

Species considered in November 2020 and placed in the Data Deficient category.

Introduction to part two

Southern British Columbia (BC) Chinook Salmon comprise 28 Designatable Units (DUs). The focus of this Part Two report is the 12 DUs that are considered to have had more extensive artificial enhancement, usually through hatchery production. Please refer to Part One report (COSEWIC 2018) for the status of the other 16 DUs and for additional information on this report’s 12 focal DUs. The list of assessed Designatable Units in Part Two is:

DU 1: Southern Mainland Boundary Bay, Ocean, Fall population

DU 6: Lower Fraser, Ocean, Summer population

DU 13: South Thompson, Stream, Summer 1.3 population

DU 15: Lower Thompson, Stream, Spring population

DU 18: South Coast - Georgia Strait, Ocean, Fall population

DU 20: East Vancouver Island, Ocean, Summer population

DU 21: East Vancouver Island, Ocean, Fall population

DU 22: South Coast - Southern Fjords, Ocean, Fall population

DU 23: East Vancouver Island, Ocean, Fall (EVI + SFj) population

DU 24: West Vancouver Island, Ocean, Fall (South) population

DU 25: West Vancouver Island, Ocean, Fall (Nootka and Kyuquot) population

DU 26: West Vancouver Island, Ocean, Fall (WVI + WQCI) population

COSEWIC executive summary

Chinook Salmon

Oncorhynchus tshawytscha

Designatable Units in Southern British Columbia

(Part Two - Designatable Units with High Levels of Artificial Releases in the Last 12 Years)

See also part one report (COSEWIC 2018)

Technical summaries

Oncorhynchus tshawytscha

Chinook Salmon

Saumon chinook

Range of occurrence in Canada (all DUs in this report): British Columbia, Pacific Ocean

Designatable Unit 1: Southern Mainland Boundary Bay, Ocean, Fall population / Population du sud de la partie continentale (C.-B.) - baie Boundary, type océanique, automne

Threats

A threats calculator was not completed. The main threats are hatchery releases, marine survival and harvest

Status and reasons for designation:

Status history

Designated Threatened in November 2020.

Status:

Threatened

Alpha-numeric codes:

D1

Reasons for designation:

Mature fish in this population spawn in tributaries to Boundary Bay such as the Serpentine, Nicomekl and Little Campbell rivers, in southern British Columbia. This wildlife species occurs in highly altered freshwater and marine habitats. Ongoing low marine survival, bycatch, and fish culture effects are cumulative threats to the remaining wild fish. Hatchery releases are ongoing and have included fish from other populations, threatening the genetic integrity of the few remaining wild fish. While hatchery production has allowed the total population size to increase, a consensus of expert opinion estimates fewer than 1000 mature wild fish remain.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. While IAO is less than threshold for Endangered, other sub-criteria do not apply.

Criterion C (Small and Declining Number of Mature Individuals): Not applicable. No evidence for declining number of mature individuals.

Criterion D (Very Small or Restricted Population): Meets Threatened, D1. While indices of abundance of wild plus hatchery-produced spawners are increasing, consensus of expert opinion indicates that the most recent estimates of total number of mature fish at the three sites where spawning has been documented is fewer than 1000.

Criterion E (Quantitative Analysis): Not done.

Designatable Unit 6: Lower Fraser, Ocean, Summer population / Population du bas Fraser, type océanique, été

Threats

A threats calculator was not completed. The main threat is ecosystem modifications.

Status and reasons for designation:

Status history

Designated Endangered in November 2020.

Status:

Endangered

Alpha-numeric codes: B2ab(iii,v);

C2a(ii)

Reasons for designation:

Mature fish in this population return in summer and spawn at a single site (Maria Slough), in the lower Fraser River. A continuing decline in spawner abundance is expected as a result of highly modified freshwater and marine habitats, low marine survival and harvest. Failed water control structures and low water levels prevented spawners from accessing the spawning site in 2018. A continuing decline in water quality and quantity is expected due to increasing urbanization and runoff.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable. No information is available to disaggregate hatchery and wild fish trends. The trends in population abundance are difficult to interpret due to the past influence of hatchery releases.

Criterion B (Small Distribution Range and Decline or Fluctuation): Meets Endangered, B2ab(iii,v), because the IAO is less than the threshold, there is only one location, and continued deterioration in habitat quality is predicted to lead to a continued decline in the number of mature individuals.

Criterion C (Small and Declining Number of Mature Individuals): Meets Endangered, C2a(ii), as the remaining number of spawners is less than the threshold, inferred declines in abundances are expected to continue, and only one subpopulation exists.

Criterion D (Very Small or Restricted Population): Meets Threatened, D1, as the number of mature individuals is less than the threshold, and Threatened, D2, as there is a single location, prone to the effects of human activities and stochastic events, and the population could become Critically Endangered or Extinct within 1-2 generations. Although D1 and D2 Threatened were met, the species was determined to be more at risk and Endangered under criteria B and C.

Criterion E (Quantitative Analysis): Not applicable. Not done.

Designatable Unit 13: South Thompson, Stream, Summer 1.3 population / Population de la Thompson Sud, type fluvial, été 1.3

Threats

A threats calculator was not completed but the threats calculator for DU 15 (Lower Thompson, Stream, Spring population) may be used as a proxy. The main threats are ecosystem modifications, marine survival, invasive species, avalanches/landslides, and droughts.

Status and reasons for designation:

Status history

Designated Endangered in November 2020.

Status:

Endangered

Alpha-numeric codes:

C2a(ii)

Reasons for designation:

Mature fish in this population migrate up the Fraser River in summer, through the Thompson River to spawn in major Shuswap Lake tributaries such as the Seymour, Eagle, Scotch and the Salmon rivers. The estimated number of remaining wild spawners is fewer than 2500 fish, and there is a projected continuing decline in numbers. Threats include decreased water levels (water withdrawal and changes in volume as a result of low marine survival, harvest, and timing of snow melt), agricultural runoff, pollution from transportation accidents, and highly modified freshwater habitats. Such threats are accentuated due to a relatively long freshwater residence.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable. Close to meeting threshold for Threatened, A2bd: while the point estimate of the decline rate over the last three generations is 22%, the probability that the decline rate is actually >30% is 0.4.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. Does not meet the criterion.

Criterion C (Small and Declining Number of Mature Individuals): Meets Endangered, C2a(ii), as a consensus of expert opinion indicates that the remaining number of spawners is less than the threshold, there is an anticipated continuing decline, and only one subpopulation.

Criterion D (Very Small or Restricted Population): Not applicable. Thresholds exceeded.

Criterion E (Quantitative Analysis): Not applicable. Not done.

Designatable Unit 15: Lower Thompson, Stream, Spring population / Population de la Thompson inférieure, type fluvial, printemps

Threats

A threats calculator was completed. The main threats are ecosystem modifications, marine survival, hatchery releases, invasive species, avalanches/landslides, and droughts.

Status and reasons for designation:

Status history

Designated Endangered in November 2020.

Status:

Endangered

Alpha-numeric codes:

A4bcde

Reasons for designation:

Mature fish in this population migrate up the Fraser River in spring to the Thompson River and then into the Nicola, Deadman and Bonaparte rivers to spawn. Marine survival has been low since 2000. There has been a steep decline in the number of mature individuals from 2013 to 2018. This wildlife species faces a number of continuing and severe threats in its freshwater and marine habitat, including post Pine Beetle deforestation, short and long-term effects from wildfires (the large Elephant Hill fire occurred here in 2018), habitat destabilization, and climate-change induced disruption to water quality. Agriculture water withdrawal is substantial and ongoing.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Meets Endangered, A4bcde, as there is an observed past and future inferred population size reduction of more than 50% based on estimated numbers (b), and ongoing and projected declines due to habitat deterioration and decreased marine survival (c), continuing harvest (d), and increased competition at sea with hatchery-origin fish (e).

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. Thresholds exceeded.

Criterion C (Small and Declining Number of Mature Individuals): Meets Threatened, C2a(ii), as the remaining number of spawners is less than the threshold, there is an anticipated continuing decline and only one subpopulation occurs. Although C2a(ii) Threatened was met, the species was determined to be more at risk and Endangered under criterion A.

Criterion D (Very Small or Restricted Population): Not applicable. Thresholds exceeded.

Criterion E (Quantitative Analysis): Not applicable. Not done.

Designatable Unit 18: South Coast - Georgia Strait, Ocean, Fall population / Population de la côte sud - détroit de Georgia, type océanique, automne

Threats

A threats calculator was not completed. The main threat is hatchery releases.

Status and reasons for designation:

Status history

Species considered in November 2020 and placed in the Data Deficient category.

Status:

Data Deficient

Alpha-numeric codes:

Not applicable

Reasons for designation:

Mature fish in this population return in the fall to rivers flowing into the south coast inlets of the Salish Sea between Burrard Inlet near Vancouver and Toba Inlet to the north. Abundance trend information is available for only two of 19 sites within the range of this relatively remote and poorly documented wildlife species. While these show a stable trend from 2005 to 2018, spawning is thought to occur elsewhere in the northern area. Data are too few to determine status.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Too few data to apply criterion.

Criterion B (Small Distribution Range and Decline or Fluctuation): Too few data to apply criterion.

Criterion C (Small and Declining Number of Mature Individuals): Too few data to apply criterion.

Criterion D (Very Small or Restricted Population): Too few data to apply criterion.

Criterion E (Quantitative Analysis): Not done.

Designatable Unit 20: East Vancouver Island, Ocean, Summer population / Population de l’est de l’île de Vancouver, type océanique, été

Threats

A threats calculator was completed. The main threats are ecosystem modifications, drought, exploitation, marine survival and hatchery releases.

Status and reasons for designation:

Status history

Designated Endangered in November 2020.

Status:

Endangered

Alpha-numeric codes:

C2a(ii)

Reasons for designation:

Mature fish in this population return in summer to spawn in the upper reaches of rivers draining the east side of Vancouver Island, from the Koksilah River in the south to the Puntledge River in the north. According to a consensus of expert opinion, fewer than 1000 wild spawners remain in this population. Exploitation rates are relatively high (about 40%), and marine survival estimates have been low for many years. Additional threats include ecosystem modifications (dam construction and channelization) and drought. The contribution of fish from hatcheries confounds the determination of population trends; hatchery-origin spawners may be a continued threat through direct competition and gene flow.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable. Available indices of abundance over the most recent three generations and over longer time spans show conflicting trends that are difficult to reconcile.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. While the IAO is less than the threshold for Endangered, other sub-criteria do not apply.

Criterion C (Small and Declining Number of Mature Individuals): Meets Endangered C2a(ii), as the estimated remaining number of spawners is less than the threshold, declines are expected to continue, and only one subpopulation exists.

Criterion D (Very Small or Restricted Population): Meets Threatened, D1, given that there are fewer than 1000 mature individuals estimated. Thresholds for Threatened D2 are exceeded. Although D1 Threatened was met, the species was determined to be more at risk and Endangered under criterion C.

Criterion E (Quantitative Analysis): Not applicable. Not done.

Designatable Unit 21: East Vancouver Island, Ocean, Fall population / Population de l’est de l’île de Vancouver, type océanique, automne

Threats

A threats calculator was completed. The main threats are hatchery releases, harvest marine survival.

Status and reasons for designation:

Status history

Designated Special Concern in November 2020.

Status:

Special Concern

Alpha-numeric codes:

Not applicable

Reasons for designation:

Mature fish in this population return in fall to the east side of Vancouver Island to spawn in multiple rivers from the Goldstream near Victoria north to Campbell River. Five of the six watersheds within the range of this wildlife species are mostly inhabited by hatchery-origin fish. While the overall abundance in the single remaining watershed is increasing, several large-scale hatcheries aim to augment production within the other watersheds and straying could pose threats from competition and gene flow to the remaining wild fish. Other threats include low marine survival, relatively high exploitation rates, ecosystem modifications and water management/use. This wildlife species could become Threatened if these factors are not properly managed.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable. Information is available to disaggregate hatchery and wild fish trends and abundance of wild fish has been increasing.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. While the IAO is less than the threshold for Threatened, other sub-criteria do not apply.

Criterion C (Small and Declining Number of Mature Individuals): Not applicable. No evidence for declining number of mature individuals.

Criterion D (Very Small or Restricted Population): Not applicable. Exceeds thresholds for D1 and D2.

Criterion E (Quantitative Analysis): Not applicable. Not done.

Designatable Unit 22: South Coast - Southern Fjords, Ocean, Fall population / Population de la côte sud - fjords du sud, type océanique, automne

Threats

A threats calculator was not completed. The main threats are harvest, marine survival and hatchery releases.

Status and reasons for designation:

Status history

Species considered in November 2020 and placed in the Data Deficient category.

Status:

Data Deficient

Alpha-numeric codes:

Not applicable

Reasons for designation:

Mature fish in this population return in the fall to the fjords of the Phillips Arm and Bute Inlet near Johnstone Strait in southern BC. Spawners migrate to the remote habitats of the Phillips, Franklin, Orford, and other rivers. While some survey information exists, coverage is incomplete and changes in methodology make it difficult to interpret trends in abundance or recent numbers of mature individuals. Data are too few to assess status.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Too few data to apply criterion.

Criterion B (Small Distribution Range and Decline or Fluctuation): Too few data to apply criterion.

Criterion C (Small and Declining Number of Mature Individuals): Too few data to apply criterion.

Criterion D (Very Small or Restricted Population): Too few data to apply criterion.

Criterion E (Quantitative Analysis): Not done.

Designatable Unit 23: East Vancouver Island, Ocean, Fall (EVI + SFj) population / Population de l’est de l’île de Vancouver, type océanique, automne (EVI + SFj)

Threats

A threats calculator was completed. The main threats are dams and water management/use, harvest, marine survival, hatchery releases.

Status and reasons for designation:

Status history

Designated Not at Risk in November 2020.

Status:

Not at Risk

Alpha-numeric codes:

Not applicable

Reasons for designation:

Mature fish in this population return in fall to spawn in rivers which drain the eastern slope of Vancouver Island’s coastal mountain ridge, such as the Adam, Quinsam, Nimpkish, Salmon and Campbell Rivers. While the population faces a number of threats including competition and gene flow from hatchery production, indices of abundance suggest increasing numbers.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable. Information is available to disaggregate hatchery and wild fish trends; estimated abundance of wild fish has been increasing. However, the influence of hatchery origin spawners in the Quinsam River is high.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. While the IAO is less than the threshold for Endangered, other sub-criteria do not apply.

Criterion C (Small and Declining Number of Mature Individuals): Not applicable. No evidence for declining number of mature individuals.

Criterion D (Very Small or Restricted Population): Not applicable. Exceeds thresholds for Threatened, D1 and D2.

Criterion E (Quantitative Analysis): Not applicable. Not done.

Designatable Unit 24: West Vancouver Island, Ocean, Fall (South) population / Population de l’ouest de l’île de Vancouver, type océanique, automne (sud)

Threats

A threats calculator was completed. The main threats are hatchery releases, ecosystem modifications, agricultural and forestry effluents, harvest and marine survival.

Status and reasons for designation:

Status history

Designated Threatened in November 2020.

Status:

Threatened

Alpha-numeric codes:

C2a(ii)

Reasons for designation:

Mature fish in this population return in fall to spawn at a large number of sites in rivers along the south west coast of Vancouver Island including the Nahmint, San Juan, Somass-Sproat, Nitinat, and Sarita Rivers. Survey information is available for many spawning locations, and while the overall trends are unclear, <10,000 wild adults are thought to remain. Large-scale hatcheries operating with the aim of augmenting production have resulted in straying of hatchery-origin spawners throughout the range. Such straying likely compromises the genetic composition of spawners and therefore represents a continuing threat to the wildlife species. Other threats include ecosystem modifications (primarily due to slides and sedimentation from forestry) and aquaculture of Atlantic Salmon, all of which are inferred to result in a future decline in numbers of wild fish.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable. Available indices of abundance over the most recent three generations and over longer time spans show conflicting trends that are difficult to reconcile.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. While the IAO is less than the threshold for Threatened, other sub-criteria do not apply.

Criterion C (Small and Declining Number of Mature Individuals): Meets Threatened, C2a(ii), as a consensus of expert opinion indicates there are fewer than 10,000 wild mature individuals, threats, based on expert opinion, are expected to continue, and only one subpopulation exists.

Criterion D (Very Small or Restricted Population): Not applicable. Exceeds thresholds.

Criterion E (Quantitative Analysis): Not applicable. Not done.

Designatable Unit 25: West Vancouver Island, Ocean, Fall (Nootka and Kyuquot) population / Population de l’ouest de l’île de Vancouver, type océanique, automne (Nootka et Kyuquot)

Threats

A threats calculator was completed. The main threats are hatchery releases, ecosystem modifications, harvest, marine survival, tourism/recreation areas, industrial effluents, agriculture/forestry issues, avalanches/landslides and droughts.

Status and reasons for designation:

Status history

Designated Threatened in November 2020.

Status:

Threatened

Alpha-numeric codes:

C2a(ii)

Reasons for designation:

Mature fish in this population return in fall to the remote Nootka and Kyuquot Sounds on the west coast of Vancouver Island. They spawn in larger rivers such as the Conuma, Gold, Tahsish, and Zeballos Rivers. While this wildlife species spawns at a large number of sites, with survey information being available from many spawning areas, population trends are most likely heavily influenced by hatchery releases aimed to augment natural production. Straying of hatchery-origin spawners has been documented throughout the range and is expected to continue, likely compromising the genetic composition of wild spawners. Other threats include long-term effects from forestry, mainly slides and sedimentation.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable. Available indices of abundance over the most recent three generations and across longer time series do not show declines.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. While the IAO is less than the threshold for Endangered, other sub-criteria do not apply.

Criterion C (Small and Declining Number of Mature Individuals): Meets Threatened, C2a(ii). The consensus of expert opinion indicates that there are fewer than 10,000 wild, mature individuals, all within one subpopulation. A continuing decline is inferred from expert opinion. The number of mature fish based on expert opinion suggests it may meet Endangered, C2a(ii), with fewer than 2500 mature, wild fish.

Criterion D (Very Small or Restricted Population): Not applicable. Exceeds thresholds.

Criterion E (Quantitative Analysis): Not applicable. Not done.

Designatable Unit 26: West Vancouver Island, Ocean, Fall (WVI + WQCI) population / Population de l’ouest de l’île de Vancouver, type océanique, automne (WVI + WQCI)

Threats

A threats calculator was not completed. The main threat is hatchery releases.

Status and reasons for designation:

Status history

Species considered in November 2020 and placed in the Data Deficient category.

Status:

Data Deficient

Alpha-numeric codes:

Not applicable

Reasons for designation:

Mature fish in this population return in fall to the remote watersheds on the west coast of Vancouver Island, north of the Brooks Peninsula. Adults return to spawn at a number of larger rivers, such as the Goodspeed, Marble, and Klaskish Rivers. Juvenile smolt enter Quatsino Sound after a brief residency in fresh water. While this wildlife species is known to spawn at a number of sites, survey information is available from only one site. This single monitoring site is heavily enhanced by hatchery releases and likely does not represent the entire population. Data are too few to assess status.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Too few data to apply criterion.

Criterion B (Small Distribution Range and Decline or Fluctuation): Too few data to apply criterion.

Criterion C (Small and Declining Number of Mature Individuals): Too few data to apply criterion.

Criterion D (Very Small or Restricted Population): Too few data to apply criterion.

Criterion E (Quantitative Analysis): Not done.

Standard technical summary boxes 11 to 21 are not included in this report part.

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2020)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)^*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)^**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)^***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

^* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
^** Formerly described as “Not In Any Category”, or “No Designation Required.”
^*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.

Please refer to the part one report for overview sections on:

Wildlife species description and significance

Name and classification

Morphological description

Population spatial structure and variability

Designatable unit delineation methods

Special significance

Distribution

Habitat

Biology

Population sizes and trends

Threats and limiting factors

Format of designatable unit-specific chapters

Please see the DU-by-DU Technical Summaries in the front section of this report part. In the following DU-specific chapters, the information covered for each DU will include:

1. names, life-history type, run-timing and generation time
2. extent of occurrence and area of occupancy
3. habitat trends
4. abundance
5. fluctuations and trends
6. threats and limiting factors

Names, life-history type, run-timing and generation time

Each DU chapter begins by listing the full DU name, the DU short name, the Joint Adaptive Zone (JAZ) short name, the life-history type (Ocean or Stream), the run-timing type (Fall, Spring, Summer), and generation time. Run timing is the time at which adult Chinook Salmon begin their return migration to natal streams. Please refer to the Part One report (COSEWIC 2018) for a more detailed explanation of the run-timing definitions used to classify southern BC Chinook Salmon populations. Generation time is estimated as the average age of spawners in the absence of fishing mortality. These figures are based on coded-wire tag (CWT) indicator stocks (shown in Table 3). Where indicator stocks are not available within a DU, proxy indicator stocks are used. For southern BC Chinook Salmon DUs, all the CWT indicator stocks are integrated hatchery stocks. Because both natural and hatchery origin fish are used as brood stock and CWTs are applied to their progeny, it is assumed that other natural origin fish in the DU are represented reasonably by the indicator stocks. This assumption is often made with southern BC Chinook Salmon, but it is well known that these indicator stocks were chosen by convenience, and not by random selection or any other manner intended to accurately represent the characteristics of the conservation unit. The extent to which these indicator stocks represent other stocks within a given DU is unknown. These are currently the best data available for the purpose of estimating generation time (G. Brown pers. comm. 2019).

Extent of occurrence and area of occupancy

For each DU, Extent of occurrence and area of occupancy data are reported at the DU level of analysis (see the Designatable Unit Delineation section of this report). The spatial extent of all DU boundaries is shown in Figure 1, this coverage represents the terrestrial (i.e., freshwater) extent of occurrence for the southern BC Chinook Salmon assessed in this report.

DU boundary delineations were adapted from Conservation Unit (CU) Report Cards developed by Porter et al. (2013) which used third-order plus watersheds from the 1:50,000 British Columbia Watershed Atlas as a base spatial scale of analysis. Prior to release of the Porter et al. report, some of these CU boundaries were modified to allow for Fisheries and Oceans Canada (DFO)-defined changes; as a result, associated metrics were recalculated. Generally, DU boundaries used in this report correspond to CU boundaries. In the cases of DU12 and DU21, multiple CUs comprise the DU. For DU-specific chapters, individual DU areal extents are estimated in GIS software using geospatial shapefiles. The DU map in Figure 1 is confirmed as up-to-date and accurate as of 2012. However, after the release of the Porter et al. report, the spatial extents of the CU areas were again redefined - in all cases they were expanded. At the time of writing, data were unavailable for these revised boundaries.

The marine extent of Chinook Salmon cannot be precisely defined geospatially due to lack of available data, but the extent of occurrence for all southern BC Chinook Salmon is known to be >20,000 km². According to harvest statistics, Chinook Salmon ocean ranges extend northward to southeast Alaska (Riddell et al. 2013). Ranges specific to southern BC Chinook Salmon vary depending on life-history strategy with ‘local’ stocks moving as far north as central Queen Charlotte Islands and as far south as the Columbia River mouth (R. Bailey, pers. comm., 2019). “Offshore” stocks are believed to range as far north as the Bering Sea and into the North Pacific Gyre (R. Bailey, pers. comm., 2019).

Following methods used for the COSEWIC Fraser Sockeye Salmon Status Report, the Indexed Area of Occupancy (IAO) for each DU is calculated as two times the spawning length, and is reported in square kilometres. This method is equivalent to overlaying a 2×2km square grid over the stream, and adding up the total area. To assist in comparison across DUs, each DU description also states the DU’s proportion of spawning habitat relative to the total across all southern BC Chinook Salmon DUs. Chinook Salmon spawning extents were provided by the BC Fisheries Information Summary System (FISS), and are meant to cover the total linear length of known Chinook Salmon spawning habitat within each DU. FISS presently represents the best available data in GIS format; however, the database is known to be incomplete due to a lack of comprehensive source information for southern BC Chinook Salmon distributions (Porter et al. 2013).

As indicated in the DU-specific sections that follow, in some instances the IAO was less than the thresholds identified in COSEWIC’s Quantitative Criteria (Appendix E3, Operations and Procedures Manual, COSEWIC). However, other subcriteria must also be satisfied to invoke status based on spatial extent. For example, the concept of “locations” is important, and refers to a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The Marine Fishes Species Specialist Subcommittee (SSC) considered this concept and concluded that given the complex life history and management structures of Chinook Salmon, that the “locations” concept does not apply. An exception is DU 6, however, where the entire population is impacted by a failing water control structure.

Figure 1. Spatial extent of the freshwater area for all southern BC Chinook Salmon Designatable Units (based on Conservation Unit delineations, which are being regularly updated by Fisheries and Oceans Canada. These boundaries are up-to-date and accurate as of 2012. No official updates have been published since that date).

Habitat trends

Habitat trends reported for each DU’s freshwater-based area describe some of the known indicators adapted from the Porter et al. (2013) DFO Report Card data. Reported trends include land-based habitat alteration, urban development, rural development, mining, road density, the number of stream crossings, riparian habitat disturbance, forest disturbance, and Mountain Pine Beetle-affected pine stands.

Sampling effort and methods

Abundance

While total abundance is the most desirable metric for this category, such data are unavailable for many DUs. Hence, both this Part Two report and the Part One report (COSEWIC 2018) rely on escapement data. Escapement, defined as the number of fish arriving at a natal stream or river to spawn (also termed ‘spawner abundance’) can be assessed by presence/absence, relative abundance, or total (“true”) abundance. The New Salmon Escapement Database System (NuSEDS) is a centralized database that holds adult salmon escapement data used by DFO. Escapement data used for the status metrics in this Part Two report and the Part One report (COSEWIC 2018) originated from NuSEDS, with the understanding that not all escapement data from NuSEDS represent absolute abundances.

Escapement data quality and quantity varies across DUs and over time. In 2013, DFO undertook a process to determine thresholds for data quality of escapement data that included a three-day workshop in February of that year. The NuSEDS Estimate Classification scheme (Table 1) was central to selecting data considered to be sufficient in quality and completeness to be used for calculation of status metrics. The process is described in greater detail in Brown et al. (2013b), but it is also described briefly here. Data considered suitable for use were Type-1 through Type-4 estimates only (‘true abundance’ and ‘relative abundance’). When using the NuSEDS Estimate Classification scheme, over 61% of escapement records between 1953 and 1995 were excluded due to missing Estimate Classification information, and therefore marked as ‘unknown’. DFO identified the missing data as a high priority for ‘data rescue’. The NuSEDS Estimate Classifications were further grouped into high, moderate, low, and unknown categories: H (High) = True Abundance (Type 1 or 2), M (Mod) = Relative Abundance (Type 3 or 4), L (Low) = Relative Abundance (Type 5) or Presence/Absence (Type 6), and ? (Unknown) = Type Unknown is reported in the database or is blank.

Within a DU or, in the case of the Wild Salmon Policy (WSP), within a CU, a key challenge is how to combine data for ‘true abundance’ (Type 1 or 2) with data for ‘relative abundance’ (Type 3 or 4). In many cases where multiple spawning sites existed, relative abundance estimates were summed with true abundance estimates to arrive at total abundance within the DU. In these cases, the entire DU was considered a ‘relative abundance index’. Under the WSP CUs, there were 4 CUs that were considered to provide actual abundance: CK-03, CK-15, CK-21, and CK-22. However, when combined into DUs, only DU2 (CK-03) was considered to provide actual abundance (CK-15 is combined into DU12 with CK-13; CK-21 and CK-22 are combined into DU 21 with CK-25 and CK-27). In both relative abundance index and actual abundance cases, all CUs/DUs had considerable past and current enhancement (Brown et al. 2013b). See also Part One (COSEWIC 2018) for more discussion of the relationship between DU and CU.

Sample sites within a DU were assessed based on the quality and completeness of their time series. The full list of sample sites is presented in Appendix 1 along with start/end dates for each estimation method. Note that sites with very low contributions are not included in the figures reported in Panels c and d of the ‘abundance, enhancement, and hatchery release’ data graphics (Figure 2) of each DU chapter (e.g. Wap Creek in DU12). The process is described in greater detail by Brown et al. (2013), and relied on the following criteria:

1. Sites must be ‘persistent’. ‘Persistent’ sites (‘P’) were defined as those having more than 50% high quality observations (Type-1 to Type-4) during the period Start Year to the last available year, with no more than one generation of years missing in sequence. For example, for DUs with a start year of 1995, this translates into at least 10 years of high quality data from the period that was part of the in-depth data review, and no more than 3, 4, or 5 years in a row missing (depending on the average generation time for the DU) for each persistent census site in the DU.
2. For sites with marginal numbers of high quality observations during the Start Year to the last available year, the pattern of missing data was investigated to determine if it could be infilled to provide a sufficiently complete time series (i.e., the pattern of missing observations for the census site did not include a full generation-based on the average generation time for the DU-at any point in the Start Year to the last available year). Those that could meet the sufficiency criteria with infilling were identified as ‘P’, and the rest were classified as data deficient (‘DD’).
3. If a site had 50% or fewer high-quality observations during the Start Year to the last available year and could not be infilled to achieve a 50% level, it was categorized as ‘DD’.

If a DU had no persistent sites, it was deemed by the Department of Fisheries and Oceans to be data deficient (DD, note that this designation is not the same as the COSEWIC usage).

When combining data from more than one site within a CU that contained years with missing data, infilling was performed by DFO. This process is described in greater detail in Brown et al. (2013b). Infilling followed the procedure outlined in English et al. (2006), whereby the average proportion (across years) each census site contributed to the total was calculated, and used to infill years with no escapement data. When the time series of several CUs within a DU were combined (i.e., DU12 and DU21), the same English et al. (2006) approach was adopted. Table 2 summarizes data treatment stages and differences between the procedures used for the Part One report (COSEWIC 2018) and this Part Two report.

CWT are used as a source of detailed information for many populations of Chinook Salmon along the Pacific coast of North America (Hankin et al. 2005; Nandor et al. 2010). Chinook Salmon populations with consistent annual releases of CWTs are referred to as CWT indicator stocks and are used to represent naturally spawning wild stocks which exhibit the same adult and juvenile life-history patterns and are assumed to exhibit the same behavioural patterns within a similar geographic area. To produce sufficient CWTs for analysis, most of the CWT indicators are tied to hatchery programs, where fish are reared, tagged, and released. There are 11 Canadian CWT indicator stocks distributed among southern BC Chinook Salmon DUs (Table 3). Most of these stocks are from large-scale conventional hatchery facilities with four located within the Fraser River drainage (DU2, DU11, DU12, DU15, and the Chilliwack River) and five distributed around Vancouver Island (DU20, DU21, DU23, and DU24). Two CWT programs were terminated in the early 2000s (DU11 and DU21 - Nanaimo River) but funds administered by the Coded Wire Tag Improvement Team of the Pacific Salmon Commission (PSC) have been used recently to improve aspects of the others (PSC-CTC 2012a).

Information provided by CWTs includes ocean distribution (via catch of tagged fish vulnerable to fishing gear), exploitation, smolt-to-adult survival, and mean age at maturity. The Pacific Salmon Treaty (PST) between Canada and the United States supports annual sampling programs to collect information from CWT indicator stocks using a consistent and unbiased design (Brown et al. 2013b). Information from CWT indicator stocks is obtained from the cohort analysis output files, which extend to the end of 2012, and were used to produce the Chinook Salmon Technical Committee (CTC) 2013 annual report (Brown et al. 2013b). The details of the cohort analysis procedure are described in PSC-CTC (1987).

Identification of wild origin fish

A key consideration for the 12 DUs considered here is how hatchery and wild-origin fish were identified. DFO uses two methods to identify hatchery-origin spawners. The first is the use and detection of fish carrying CWTs, as described earlier. The second is manipulation of hatchery water temperature regimes which result in marks on the otoliths of fish. In both instances, estimation of the relative contribution of hatchery and wild origin returning mature fish is contingent on a well-designed sampling program that covers all known spawning areas within the DU and an understanding of the fraction of releases that are marked.

“Wild” fish are here defined as 2^nd generation wild spawners, consistent with the definition used in DFO’s Wild Salmon Policy. Wild abundances are derived from total abundances x (pNOS x pNOS), where pNOS is the proportion of Natural Origin Spawners on the spawning grounds, and pNOS x pNOS is the proportion of the total abundances with parents that were both natural-origin spawners assuming random mating and equal survival. For example, if you have two wild males, two wild females, one hatchery male and one hatchery female, there are six possible mating combinations for three pairs of males and females. In this case, 44.4% of the mating combinations are wild fish. As the wild fish were 66.7% of the population (in this example), 66.7² = 44.4%.

The Proportional Natural Influence (PNI) metric is reported as a measure of hatchery influence on the wild population, when such data are available for each DU (Appendix 1). The metric is formulated as:

If a “wild population” is a population that contains predominantly “wild” fish, then large scale hatchery production is a clear threat as it will reduce the number of second-generation natural spawners and increase the number of hatchery-origin spawners. This effect should be reflected in the index of wild spawners described above; as hatchery production goes up, the average proportion of natural origin spawners (pNOS) goes down and hence the number of “wild” spawners. However, there are at least five reasons why this metric of “wild” spawners may not reflect true “wild” spawners in some circumstances, as calculated in this report.

(1) DU-specific time-series of spawner abundances are derived by summing abundances from all component persistent sites, with infilling, over time. Only sites that have been persistently monitored for approximately the last 3 generations are included in the summation. For some DUs, monitoring has been stopped or reduced at sites where natural spawning occurred historically, e.g., 1980s and 1990s, but no longer occurs in some cases because of introgression from neighbouring hatcheries and an associated reduction of fitness. The loss of natural spawning is therefore not captured in the time series of “wild” spawner abundances. DUs 24 and 25 on the west coast of Vancouver Island are two examples.

(2) Long and consistent time-series of pNOS are not available for most populations. In the absence of consistent annual pNOS values (and to smooth across sampling variability), long-term averages have been applied to estimate “wild” spawners. Without annual time-series on pNOS the trends in the metric of “wild” spawners do not capture changes in the proportion of “wild” fish due to increases (or decreases) in hatchery production relative to natural production over the time-series. In some cases (DU24, DU25 on the west coast of Vancouver Island), increases in the metric of “wild” abundances reflect increases in hatchery production relative to natural production that may be masking declines in “wild” fish.

(3) When hatchery production is high relative to natural production and proportionate natural influence (PNI) is low, all fish in the population are poorly adapted to the natural environment. Even if there are second-generation spawners in the system, they may have poor survival being adapted to the hatchery environment and may not be able to sustain a population over the long-term (as described for DU24 and DU25 by local DFO biologists).

(4) DFO has no way of marking 2^nd generation spawners and the calculations assume progeny of 1^st-generation natural-origin spawners survive to the next generation. When hatchery production is large, hatchery-origin fish will dominate in the natural spawning environment with some first-generation natural origin spawners. Although these first generation spawners may be numerically significant (but <50%) they may not sustain a population due to low survival of their progeny in the natural environment (point 2 above). In particular, there may be a higher proportion of first generation natural origin than 2^nd generation spawners than expected under equal survival because of hereditary genetic and epigenetic factors from introgression that can extend over numerous generations. Without marking of 2^nd generation spawners, there may be an overestimation of this proportion due to poor survival.

(5) Within some DUs (DU 6,18, 21 and 26), there are sites that are artificially enhanced, but no measures of the proportion of wild and hatchery-origin spawners are available. For such sites, the current process assumes that all spawners from such sites are natural origin fish.

Given these considerations, it becomes important to assess the utility of the index of wild fish abundance on a DU by DU basis. Within each of the DU-specific chapters that follow, guidance is provided on how to interpret the trends in the abundance of wild fish.

Enhancement

Wild-born fish cannot be distinguished from their hatchery counterparts with certainty unless mass marked. However, mass marking is not currently employed in Canada for Chinook Salmon (only hatchery Coho Salmon). Therefore, the authors of the pre-COSEWIC report adopted a higher-level approach based on categorizing sites by enhancement activity level (Brown et al. 2013b). Census sites within DUs were assigned a level of enhancement based on a standardized procedure developed by DFO during the pre-COSEWIC process (Brown et al. 2013b). The standardized rank classified the census sites as:

• category 1. Unknown (no evidence of recent active enhancement) - no release records, brood records or enhanced contribution estimates during the period 2000-2011
• category 2. Low enhancement activity level - release records, brood records or enhanced contribution estimates exist prior to 2000 but there were none from 2000-2011
• category 3. Moderate enhancement activity level, defined as:
  • number of release records is less than or equal to 4 out of 12 years (≤25% or roughly 1 per generation)
  • number of brood take records are less than or equal to 4 out of 12 years (≤25% or roughly 1 per generation)
  • hatchery-origin contribution estimate is available via expanded CWT data and 12-year mean is <25% (assessing adult contribution only). Note that otoliths are also used to examine hatchery-origin contributions at some sites
• category 4. High enhancement activity level, defined as:
  • number of release records exceeds 4 out of 12 years (>25% or >1 per generation)
  • number of brood take records exceeds 4 out of 12 years (>25% or >1 per generation)
  • hatchery-origin contribution estimate is available via expanded CWT data and 12-year mean is ≥25% (assessing adult contribution only). Note that otoliths are also used to examine hatchery-origin contributions at some sites

For each DU-specific chapter, a figure is presented showing the proportion of spawners originating from wild-born and enhanced census sites. These figures are updates to the Part One report (COSEWIC 2018) and the 2015 figures developed for the pre-COSEWIC report (Brown et al. 2013b), and are adapted from CU-level time series of escapement for wild and enhanced sites. Where multiple CUs are combined to form a DU (e.g., DU21), figures for each individual CU are included. In developing these figures, CU-level time series of escapement for wild-born sites and enhanced sites were created. Data were combined from sites with low or unknown levels of enhancement (‘Low+Unk’) and sites with moderate or high levels of enhancement (‘Mod+High’). The estimated proportion of natural origin spawners based on pNOS adjustments are also presented (see Figure 2 and Table 4).

Hatchery releases

For each DU, the time series of hatchery releases from within the DU and/or from outside the DU are presented. These are reproductions of the ‘dashboard’ graphics found in Brown et al. (2013b). When a DU is a combination of several CUs (e.g., DU21), the time series for each individual CU is included. Hatchery release data are not currently disaggregated by life history stage at release. Therefore, it is important to note that release data for different life stages are not comparable.

Interpretation of abundance, enhancement and hatchery release data

Data permitting, enhancement, wild population, and hatchery release data are presented graphically for each DU as a four-panel figure (see example for DU22 / CU28 below). Table 4 describes how to interpret each panel:

Figure 2. Example of graphical presentation for abundance, enhancement and hatchery release data.

The following table explains how to interpret each panel and can be used as a guide while reviewing each DU.

Fluctuations and trends

For each DU, Fluctuations and trends are presented in a summary table and two six-panel figures. The summary table provides two Bayesian estimates of changes in spawner abundance: one using the last three generations of data, and the other using the entire time series of data. Probabilities of a 30%, 50%, and 70% decline in spawner abundance for each of the two Bayesian estimates of change in spawner abundance are also presented. These results are provided for both the unadjusted population and the pNOS adjusted population, which represents trends in wild spawner abundance. For the Part One report (COSEWIC 2018), abundance data were available for most of the 28 DUs up to the 2015 return year and were provided by DFO (Gayle Brown, pers. comm. 2019). For this Part Two report, abundance data were available for the 12 focal DUs up to either the 2017 or 2018 return year and were also provided by DFO. Note that DU18 was considered data deficient for the Part One report (COSEWIC 2018) but data are now available and are included in this report.

The summary table for each DU has the following form (categories described in Table 6):

Table 5. Summary table format for Fluctuations and trends section.

In the Part One report (COSEWIC 2018) (relatively lightly enhanced DUs), trends in spawner abundance, exploitation rate and smolt-to-adult survival are presented graphically for each DU as a five-panel figure (see example for DU24 below). For the Part Two report, an additional panel is added that shows the proportional contribution by site to each DU. As per the data screening procedures described above, only sites classified as ‘Persistent’ are included. In each DU chapter, the new six-panel figure is provided twice - once for unadjusted abundance data and once for pNOS adjusted abundance data. Table 7 describes how to interpret each panel:

Figure 3. Example of graphical presentation for trends in spawner abundance, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance for DU24 (version adjusted by average proportion of natural origin spawners).

For each of the twelve DUs addressed in this report (Part 2), Appendix 1 provides a graphic for site-level survey data quality (all sites), and information on Proportionate Natural Influence (PNI) by site, where available.

Where available, stock productivity data (recruits per spawner) are also presented. Stock productivity was calculated as the total number of adults recruiting to the population (i.e., spawners + catch) produced by the spawners from a given year (brood year). Only two time series of stock productivity data are available, for DU2 and DU22 (Brown et al. 2013b). The methods used to generate these productivity time series were based on Canadian Science Advisory Secretariat (CSAS) reports (Tompkins et al. 2005, G. Brown, DFO, unpublished data). Data used for these time series were provided by DFO (Cowichan River time series: M. Labelle, DFO, unpublished data; Harrison River time series: G. Brown, DFO, unpubl. data).

Subpopulation structure

In its 2019 meeting, the Marine Fishes SSC noted that while many spawning components usually exist within a given Designatable Unit, straying is well documented among such components. Given COSEWIC’s definition of subpopulations − “As used in Criteria B and C, Subpopulations are defined as geographically or otherwise distinct groups in the population between which there is little demographic or genetic exchange (typically one successful migrant individual or gamete per year or less)” - the SSC concluded that the subpopulation concept does not apply. This conclusion impacts the interpretation of population status using COSEWIC Quantitative Criterion C2 (Small and Declining Number of Mature Individuals), where subpopulation structure must be known.

The role of expert opinion

Given the limitations on the identification of wild and hatchery-origin fish and the impacts on trends in abundance information, expert opinion was particularly important for those DUs in this Part Two report. Apart from the significant expertise available within the Marine Fishes Species Specialist Committee (MF SSC), the SSC invited outside experts to attend their 2019 annual meeting. Those experts were often DFO salmon biologists with long-standing experience in the DUs discussed in this report and were well-versed in the available data, both from hatchery and wild populations. The SSC also benefited from the participation of many representatives from First Nations and environmental non-governmental organizations with interests in Pacific salmon.

Threats and limiting factors

See the Part One report (COSEWIC 2018) for a review of the threats facing Chinook Salmon in southern British Columbia.

Each DU is assigned a general risk rating using the International Union for Conservation of Nature (IUCN) Threats Calculator (the Calculator), a fillable Excel spreadsheet that can be completed on a DU-by-DU basis to evaluate Threats and limiting factors.

The Calculator characterizes threats to DUs based on scope, severity, and timing. Scope is defined as the percentage of the species reasonably expected to be affected by the threat within 10 years if current circumstances and trends continue. Severity is the level of damage (percent population loss) to the species from the threat that can reasonably be expected within 10 years or three generations, whichever is greater, if current circumstances and trends continue. Timing is defined as the projected and estimated duration of the threat.

Scope, severity and timing rankings are assigned based on cumulative scores for eleven different threat categories comprising forty different sub-categories. Main threat categories include:

1. residential and commercial development
2. agriculture and aquaculture
3. energy production and mining
4. transportation and service corridors
5. biological resource use
6. human intrusions and disturbance
7. natural system modifications
8. invasive and other problematic species and genes
9. pollution
10. geological events
11. climate change and severe weather

Each threat sub-category is assigned a score ranging from Negligible to Pervasive (scope), Negligible to Extreme (severity), and Insignificant/Negligible to High-continuing (timing), with uncertainty ranges and Unknown or Neutral options also available. Once scores are assigned to each sub-category, level two threats are manually rolled up into level one threats, and the population’s overall threat impact is scored as A-Very High; B-High; C-Medium; and D-Low.

Threats Calculators were produced for this report using a two-stage approach. The first stage relied on literature, document review and existing data (reported here). This method supplied relevant information regarding Threats and limiting factors for each DU and permitted the production of a preliminary set of Threats Calculator results.

Some of the metrics used to evaluate threats (e.g., harvest mortality) are based on information gathered from indicator stocks, which have CWT individuals released from hatcheries. DUs with CWT indicator stocks are listed in Table 8. For those DUs without indicator stocks, proxy indicator stocks were used.

One challenge was quantifying severity because a direct causal link could not be established between most threats/limiting factors and impacts to populations. However, in some populations, metrics (e.g., harvest) could be quantified if there was an indicator stock present. This preliminary method did not provide sufficient depth and breadth to assign final Threats Calculator grades, but it did supply useful data informing the next stage.

For the second stage, a workshop of Chinook Salmon experts was convened in Nanaimo, BC in February 2017 to apply the IUCN Threats Calculator to Southern BC Chinook Salmon. This group of experts reviewed data supplied by the first stage and added new information based on expert knowledge of different DUs. The workshop provided a rich source of data, fleshing out the previous information and permitting the completion of Threats Calculator grading for several DUs as well as the assignment of proxy DUs for other DUs that could not be completed at the workshop. Table 9 shows the full list of DUs and indicates those that had Threats Calculators completed at the workshop as well as those that were assigned proxies. Where applicable, notes regarding status, priority levels, other relevant comments, and overall Threats Calculator grades are supplied.

For DU 20, 21, 24 and 25, the threats calculators were updated by the COSEWIC Marine Fishes Specialist Subcommittee (SSC) during and shortly after their annual meeting, Aug. 19-22, 2019. The overall Threats Calculator results were updated to Very High-Very High for DU 24 (note the scoring for Element 8.3 is provisional, and requires expert validation) and Very High-High for DU 25. The overall Threats Calculator results for DUs 20 and 21 were unchanged, and remained High. All completed calculators for DUs in this Part Two report are provided in Appendix 2.

Designatable unit-specific chapters

Designatable Unit 1: Southern Mainland Boundary Bay, ocean, fall population

The average generation time for this DU is 3.8 years. These fish exhibit ocean-type life-history variants and fall run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 4. Map of DU1 - Southern Mainland Boundary Bay Ocean Fall.

DU1 is the southernmost DU on the BC mainland evaluated in this study (the Okanagan DU also reaches the Canada-US border but is not included in this report). This DU is located in the BB+GStr Joint Adaptive Zone. Freshwater habitat interfaces with the marine habitat at Boundary Bay by the Serpentine River, Nicomekl River, and the (little) Campbell River. While this DU is close to the US border, there is no known spawning within the US. The spatial extent of this DU is bounded by the Fraser River in the north (Lat. 49.20, Long. 122.81) and the 49th parallel in the south. The centroid of the DU area is at Lat. 49.05, Long. 122.83. The total area of DU1 is 405.44km², which encompasses a large proportion of urban area.

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The Indexed Area of Occupancy (IAO) is 157 km², based on a total known spawning run length of 78 km or 0.76% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is highly altered (89.4%), with urban development covering 59.9% of the DU area, agricultural/rural development comprising 28.6%, and mining development comprising 0.5%. Road density in DU1 is 6.4 km/km² with an average of 1.39 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 87.6% of the DU’s riparian habitat is disturbed. As an already highly developed area, no ongoing forest disturbance is occurring in this DU and there are no pine stands affected by the Mountain Pine Beetle.

Abundance

While spawning has been noted in three rivers, this DU has a single persistent site that is enhanced (Appendix 1). Of the years when sampling occurred, estimated mature individuals all originated from streams that had moderate to high levels of enhancement (Figure 5a). The wild portion of the population is estimated at ~30% (Figure 5b). Hatchery releases increased from the early 1980s to a maximum of ~250,000 fish annually in 2011, then declined to ~100,000 fish annually in 2013 before increasing again to ~225,000 fish in 2017 (Figure 5c). Hatchery releases from outside the DU occurred from 1990 to 2003 (Figure 5d).

Figure 5. DU1 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Fluctuations and trends

Based on the last three generations of data, the number of mature individuals increased by an estimated 121% (Upper 95% CI = 960%, Lower 95% CI = -57%) with the probability of a 30% decline at 0.03 (Table 10, Figure 6a,b). Using the entire time series of data, the number of mature individuals increased by an estimated 387% (Upper 95% CI = 1148%, Lower 95% CI = 90%) with zero probability of a 30% decline (Table 10, Figure 6a,c). The longer term increase in the total number of spawners is consistent with the overall increase in number of hatchery released Chinook Salmon (Figure 5).

For estimated wild abundance the corresponding trends are the same. Hatchery production has allowed the total number of Chinook Salmon to increase, but a consensus of expert opinion (August 2019 meeting of the Marine Fishes SSC) was that the remaining mature wild fish is less than 1000. While DFO data indicate that the average number of mature individuals remaining in 2018 are 175 and 54 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1), the SSC places the most confidence on the consensus of experts’ estimate of remaining mature wild fish.

The exploitation rate for DU1 ranged from about 20% to 40% in the 1990s, then climbed to a peak of nearly 60% in 2004, after which it dropped, fluctuating from around 30% to 50% up to 2012 (Figure 6). Smolt-to-adult survival peaked at an average rate of nearly 5% in 1994 then declined over the next decade, reaching a low of 0.5% in 2000 but increasing slightly since 2008 to 3% in 2012. Stock productivity data are not available for this DU.

Table 10. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 6. DU1 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

A Threats Calculator was not completed for this DU. For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. It should be emphasized that this DU consists of primarily hatchery-origin fish with few wild fish thought to remain (R. Bailey, pers. comm., 2019). Hatchery releases have occurred within this DU, and the genetic origin of the released fish is often from outside the DU. The SSC concluded that such releases represent a threat to the wild fish in the DU due to competition and genetic introgression.

Designatable Unit 6: Lower Fraser, ocean, summer population

The average generation time for this DU is 3.8 years. These fish exhibit ocean-type life-history variants and summer run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 7. Map of DU6 - Lower Fraser River Ocean Summer.

This DU extends from the north along Hicks Lake at Lat. 49.33, Long. 121.70 to the south at the Fraser River (Lat. 49.22, Long. 121.74). The westernmost extent occurs at Bear Mountain ridge (Lat. 49.29, Long. 121.76) and the easternmost extent occurs at Fraser River (Lat. 49.27, Long. 121.68). The DU’s centroid is at Lat. 49.23, Long 121.73 and its total area is 53.49 km². Farming is the primary land use in this DU.

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 30 km², based on a total known spawning run length of 15 km, or 0.15% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (29.3%), with urban development comprising 1.9% of the DU area, agricultural / rural development comprising 25.0%, and mining development comprising 0.07%. Road density in DU6 is 2 km/km² with an average of 0.7 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 27.7% of the DU’s riparian habitat, and 2.3% of the forest cover is disturbed. There are no pine stands in this DU affected by the Mountain Pine Beetle.

Abundance

This DU has a single persistent site that is enhanced (Appendix 1). Of the years where sampling occurred, estimated mature individuals all originated from streams with moderate to high levels of enhancement (Figure 8a). Using the pNOS adjustment method, the wild portion of the population is estimated at 100%, which is inconsistent with the DU’s enhanced status and hatchery release data shown in Figure 8c and Figure 8d. Given this contradiction, Figure 8b has been omitted (Table 4). Hatchery releases increased from the mid-1990s to 2010, with maximum releases of ~110,000 occurring in 2008 (Figure 8c). No hatchery releases are reported from outside the DU (Figure 8d).

Figure 8. DU6 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation. % pNOS Adjusted (panel (b)) cannot be calculated due to sample size limitations.

Fluctuations and trends

Based on the last three generations of data, the number of mature individuals decreased by an estimated -71% (Upper 95% CI = 95%, Lower 95% CI = -95%) with the probability of a 30% decline at 0.84 (Table 11, Figure 9a,b). Using the entire time series of data, the number of mature individuals increased by an estimated 77% (Upper 95% CI = 620%, Lower 95% CI = -56%) with the probability of a 30% decline at 0.09 (Table 11, Figure 9a,c).

Trends for wild fish are unknown because there is no information available to disaggregate wild and hatchery origin fish for the DU. A consensus of expert opinion (August 2019 meeting of the Marine Fishes SSC) was that there are fewer than 1000 mature wild fish remaining. While DFO data indicate that the average number of mature individuals remaining in 2018 is 440 (Appendix 1), the SSC places the most confidence on the consensus of experts’ estimate of remaining mature wild fish.

Harvest, smolt-to-adult survival and stock productivity data are unavailable for this DU because there is no CWT indicator stock of sufficient quality.

Table 11. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 9. DU6 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

A Threats Calculator was not completed for this DU. For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. Agricultural runoff is high. Also, Maria Slough (contained within the DU and the only site of spawning) is a paleo-channel of the Fraser River; however, recent low water flows have limited access of spawners to the spawning grounds, and a complete blockage occurred in 2018 (R. Bailey, pers. comm., 2019). As a result of this, only one “location” is considered within this DU. Periodically high Fraser River flows would have maintained the habitat complexity for spawning and rearing, but now the side channels are heavily silted and grown in by vegetation. DFO has constructed some spawning habitat in a few locations (R. Bailey, pers. comm., 2019).

Hatchery releases have occurred within this DU, and the genetic origin of the released fish is from within the DU. The SSC concluded that such releases represent a threat to the wild fish in the DU due to competition and genetic introgression.

Designatable Unit 13: South Thompson, stream, summer 1.3

Unlike DU14 (another South Thompson DU described elsewhere in this report), the average generation time for this DU at 4.5 years is typical of Chinook Salmon (4.5 yrs using Dome Creek Spring as a proxy as stated in Table 8). But similar to DU14, these fish exhibit stream-type life-history variants and summer run-timing - the title suffixes 1.2 and 1.3 are used to differentiate between these life-history strategies.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 10. Map of DU13 - South Thompson Stream Summer 1.3.

This DU consists of four geographically separated sections (Scotch Creek, Seymour River, Eagle River and Salmon River (Salmon Arm)). The northernmost section extends from the northern extent of Upper Seymour River Provincial park southward following the Upper Seymour River drainage to Seymour Arm at the north end of Shuswap Lake (N: Lat. 51.69, Long. 118.96; S: Lat. 51.24, Long. 118.97; W: Lat. 51.39, Long. 119.05; E: Lat. 51.51, Long. 118.76). The southernmost section extends southwest from the outlet of Shuswap Lake at Salmon Arm, BC along the Salmon River drainage to just west of Salmon and Rush Lakes (N: Lat. 50.72, Long. 119.34; S: Lat. 50.23, Long. 120.08; W: Lat. 50.35, Long. 120.12, E: Lat. 50.51, Long. 119.24). The eastern section includes the Eagle River drainage from Bourne Glacier in the Jordan Range and west of Probity Peak to the north, and Mt. MacPherson and Mt. English to the southeast. The drainage continues to Sicamous, BC and Shuswap and Mara Lakes in the southwest (N: Lat. 51.30, Long. 118.64; S: Lat. 50.84, 118.99; W: Lat. 50.84, 118.99; E: Lat. 50.89, 118.31). The northwestern section includes the Scotch Creek drainage from Pukeashun Mountain in the north to the outlet into Shuswap Lake near Scotch Creek, BC in the south (N: Lat. 51.26, Long. 119.35; S: Lat. 50.91, Long. 119.50, W: Lat. 51.10, Long. 119.52). The DU’s centroid is at Lat. 50.87, Long. 119.20, and its total area is 3900.64 km².

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 424 km² based on a total known spawning run length of 212 km, or 2.11% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (24.0%), with agricultural / rural development comprising 8.0% and urban development 0.9% of the DU area. Road density in DU13 is 1.7 km/km² with an average of 0.7 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 20.4% of the riparian habitat and 15.7% of the forest cover is disturbed. 5.3% of the DU’s pine stands are affected by Mountain Pine Beetle. No mining development occurs within the DU area.

Abundance

This DU has both enhanced and wild sites, and three of four sites are considered to be Persistent (Appendix 1) (Figure 11a). Of the years where sampling occurred, ~40-90% of estimated spawners originated from wild sites (low or unknown enhancement). The estimated wild portion of the population fluctuated between ~40-50%, rising as high as nearly 60% in the late 1990s/early 2000s (Figure 11b). Hatchery releases were high from 1983 to 1990, peaking at ~1,150,000 fish in 1990 then declining to less than 100,000 fish by 1994 (Figure 11c). No hatchery releases are reported from outside the DU (Figure 11d).

Figure 11. DU13 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Fluctuations and trends

Based on the last three generations of data, the number of mature individuals at three persistent sites (Salmon River, Eagle River, Seymour River) decreased by an estimated
-14% (Upper 95% CI = 106%, Lower 95% CI = -65%) with the probability of a 30% decline at 0.31 (Table 12, Figure 12a,b). Using the entire time series of data, the number of mature individuals increased by an estimated 20% (Upper 95% CI = 165%, Lower 95% CI = -45%) with the probability of a 30% decline at 0.08 (Figure 12a,c). The Eagle and Salmon river systems are the largest contributors to overall abundance (Figure 12f).

For estimated wild abundance only, the corresponding trend for the last three generations is an estimated decrease of -22% (Upper 95% CI = 90%, Lower 95% CI = -67%) with the probability of a 30% decline at 0.4 (Table 12, Figure 13a,b). For the full time series, the decrease in the number of mature individuals is -9% (Upper CI = 93%, Lower CI = -58%) with the probability of a 30% decline at 0.24 (Table 12, Figure 13a,c). The relative contribution of the Eagle River to the wild population has been less over time than its relative contribution to the population as a whole, while the reverse is true for the Salmon and Seymour river systems (Figure 12f, Figure 13f). As for overall abundance, the Eagle and Salmon river systems remain the largest contributors to the wild population. A consensus of expert opinion (August 2019 meeting of the Marine Fishes SSC) was that the remaining mature wild fish are less than 2500. While DFO data indicate that the average number of mature individuals remaining in 2018 is 1049 and 443 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1), the SSC places the most confidence on the consensus of experts’ estimate of remaining mature wild fish.

Harvest, smolt-to-adult survival and stock productivity data are unavailable for this DU because there is no CWT indicator stock.

Table 12. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 12. DU13 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Figure 13. DU13 - Spawner abundance trends adjusted by average proportion of natural origin spawners, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. Chinook Salmon experts who participated in the IUCN Threats Calculator Workshop in February 2017 recommended using the DU15 Threats Calculator as a proxy for this DU (see Table 9) with the main difference being that the juveniles in DU13 stay in freshwater for one year and utilize smaller rivers. These characteristics make the fish more vulnerable than DU15 Chinook Salmon to water management issues (esp. Salmon River), and increased development (Eagle River). In the Salmon River, for example, Chinook Salmon contend with dewatering events, agricultural runoff and rising stream temperatures (R. Bailey, pers. comm., 2019). Based on these points and DU15 results, participants concluded that DU13 should be assigned a threat impact of High-Medium (B/C). Because females in fall actively seek a mix of groundwater and surface water when selecting redd sites, the most important threats in this DU are ecosystem modifications due to climate change, cyclical marine climate events (El Niño), and resulting shifts in groundwater availability caused by changes in the volume and timing of snowmelt. Other less critical impacts include invasive species (esp. spiny-rayed fishes), avalanches/landslides, droughts, and temperature extremes.

Hatchery releases have occurred within this DU, and the genetic origin of the released fish is from within the DU. The SSC concluded that such releases represent a threat to the wild fish in the DU due to competition and genetic introgression.

Threats Calculator spreadsheets are included with this report (see Appendix 2).

Designatable Unit 15: Lower Thompson, stream, spring population

The average generation time for this DU is 4 years. These fish exhibit stream-type life-history variants and spring run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 14. Map of DU15 - Lower Thompson Stream Spring.

This DU consists of 2 geographically separated sections. The smaller of these sections to the east includes the Louis Creek drainage to the confluence of Louis Creek and the North Thompson River (N: Lat. 51.14, Long. 120.11; S: Lat. 50.75, Long. 119.90; W: Lat. 50.96, Long. 120.09; E: Lat. 51.02, Long. 119.78). The larger section to the west extends southward from Montana Creek around Bonaparte Hills to Coldwater River just north of the Coquihalla Summit Recreation Area. The westernmost extent occurs at the confluence of the Thompson River and the Fraser River, and easternmost extents occur just east of Bonaparte Lake and Lac Le Jeune Provincial Park (N: Lat. 51.45, Long. 120.6; S: Lat. 49.61, Long. 121.16; W: Lat. 50.23, Long. 121.58; E: Lat. 51.27, Long. 120.33). The DU’s centroid is at Lat. 50.38, Long. 120.98, and its total area is 12324.88 km².

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 1330 km² based on a total known spawning run length of 665 km, or 6.61% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (13.5%), with urban development comprising 0.7%, agricultural / rural development 4.0%, and mining development 0.04% of the DU area. Road density in DU15 is 1.6 km/km² with an average of 0.8 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 13.7% of the DU’s riparian habitat and 8.7% of its forest cover is disturbed. 18.1% of pine stands in the DU are affected by Mountain Pine Beetle.

Abundance

This DU has both enhanced and wild sites, and six of seven sites are considered to be Persistent (Appendix 1). Of the years where sampling occurred, the proportion of estimated spawners originating from wild sites (low or unknown levels of enhancement) increased from 0% to ~60% by 2016, with a decline to less than 40% in 2018 (Figure 15a). The estimated wild portion of the population has fluctuated at just over 50% (Figure 15b). Hatchery releases increased from 1980 to 1988, peaking at ~1,250,000 fish, then declining in 1992 to between ~220,000 and ~420,000 fish per year (Figure 15c). No hatchery releases are reported from outside the DU (Figure 15d).

Additional information on the 2018 escapements to this DU were provided by DFO (R. Bailey, pers. comm., 2019), and indicate that the 2018 escapement was one of the lowest on record since 1995. A failure of the Bonaparte River fishway is thought to be responsible for the low returns, and there were few fish observed even returning to the river or trying to ascend the broken fishway.

Figure 15. DU15 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Fluctuations and trends

Based on data from six persistent sites (see Figure 16f), the number of mature individuals increased by an estimated 47% over three generations (Upper 95% CI = 585%, Lower 95% CI = -69%) with the probability of a 30% decline at 0.15 (Table 13, Figure 16a,b). Using the entire time series of data, the number of mature individuals decreased by an estimated -68% (Upper 95% CI = -18%, Lower 95% CI = -87%) with the probability of a 30% decline at 0.95 (Table 13, Figure 16a,c). The Nicola and Bonaparte river systems are historically the largest contributors to overall abundance (Figure 16f). The interpretation of decline rates over the entire time series is possibly confounded by the peak in hatchery releases in 1989-1990.

For estimated wild abundance, the corresponding trends are the same. DFO data indicate that the average number of mature individuals remaining in 2018 are 7328 and 3758 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1).

Between 1985 and 2012, the total exploitation rate fluctuated from ~10% to ~60% (Figure 16d). The most recent exploitation rate estimate is ~24% (2012). Over the same time period (1985-2012) Smolt-to-Adult survival rates fluctuated between ~0.1% and ~13% with the most recent estimate in 2012 at ~1.2% (Figure 16e). Stock productivity data are not available for this DU.

Table 13. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 16. DU15 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. Chinook Salmon experts who participated in the IUCN Threats Calculator Workshop in February 2017 concluded that DU15 should be assigned a threat impact of High-Medium (B/C). Because females in fall actively seek a mix of groundwater and surface water when selecting redd sites, the most important threats in this DU are ecosystem modifications due to climate change, cyclical marine climate events (El Niño) and resulting shifts in groundwater availability caused by changes in the volume and timing of snowmelt. Another round of ocean survival impacts as in 2003 and 2007 could terminate groups of Chinook Salmon within the DU. Other less critical impacts include invasive species (esp. spiny rayed fishes), avalanches/landslides, droughts, and temperature extremes. Chinook Salmon in this DU also contend with dewatering events and agricultural runoff (R. Bailey, pers. comm., 2019). Agricultural water extraction and reduction of riparian habitat from cattle grazing can lead to high stream temperatures, and development of railways, gas pipelines, highways and bank stabilization projects have resulted in considerable armouring of the banks and subsequent erosion and channel meandering (R. Bailey, pers. comm., 2019).

Since the Threats Calculator Workshop, there have been events in this DU that have seriously impacted habitat quality. Expert opinion contributed during the August 2019 meeting of the COSEWIC Marine Fishes SSC indicated that recent large scale deforestation of parts of the DU to “salvage log” pine beetle timber, combined with the very large Elephant Hill wildfire, have resulted in considerable loss of hillslope stability and pool-riffle-run structure in the Bonaparte, Deadman, and Nicola rivers (the most important watersheds within the DU for Chinook Salmon production). There are now multiple large sediment wedges in both systems and between clear cutting and fire impacts, >>50% of the upslope portions of both drainages are disturbed (deforested/burned), which suggests that riparian cover and channel structure are unlikely to be successfully restored in the next 20 years (R. Bailey, pers. comm., 2019).

Hatchery releases have occurred within this DU, and the genetic origin of the released fish is from within the DU. The SSC concluded that such releases represent a threat to the wild fish in the DU due to competition and genetic introgression.

Threats Calculator spreadsheets are included with this report (see Appendix 2).

Designatable Unit 18: South Coast - Georgia Strait, ocean, fall population

The average generation time for this DU is 3.6 years. These fish exhibit ocean-type life-history variants and fall run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 17. Map of DU18 - South Coast - Georgia Strait Ocean Fall.

This DU has seven geographically separated sections and extends southeastward from Filer Creek around Mount Gilbert to Seymour River close to Mount Seymour. The westernmost extent is located at Quatam River around Mount Doogie Dowler and the easternmost extent is located at Cheakamus River around Nivalis Mountain (N: Lat. 50.86, Long. 124.25; S: Lat. 49.30, Long 123.03; W: Lat. 50.37, Long. 124.93; E: Lat. 50.01, Long. 122.68). The DU’s centroid is at Lat. 49.83, Long. 123.58, and its total area is 8262.40 km².

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 504 km² based on a total known spawning run length of 252 km, or 2.51% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (7.5%), with urban development comprising 1.4%, agricultural/rural development 0.03%, and mining development 0.004% of the DU area. Road density in DU 18 is 0.7 km/km² with an average of 0.5 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 9.0% of the DU’s riparian habitat and 6.0% of its forest cover is disturbed. 0.02% of pine stands in the DU are affected by Mountain Pine Beetle.

Abundance

While the available data are too few to draw conclusions, the available information is summarized below.

The DU is comprised only of enhanced sites (Figure 18a), and two of 19 are considered persistent (Appendix 1). Using the pNOS adjustment method, the wild portion of the population is estimated at 100%, which is inconsistent with the DU’s enhanced status and hatchery release data shown in Figure 18c and Figure 18d. Given this contradiction, Figure 18b has been omitted. Hatchery releases have occurred since the late 1970s. Releases within the DU increased steadily to a peak of ~1,750,000 in the 1990s. Since then, releases declined overall to less than 100,000 fish in 2017 (Figure 18c). Hatchery releases from outside the DU occurred between 1983 and 2013, reaching a maximum of ~675,000 fish in 1989 and dropping to ~40,000 fish by 2003 (Figure 18d)^{Footnote 1}.

Figure 18. DU18 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation. % pNOS Adjusted (panel (b)) cannot be calculated due to sample size limitations.

Fluctuations and trends

While the available data are too few to draw conclusions, the available information is summarized below.

Based on the relatively short time series of abundance data at two persistent sites (Squamish River and Cheakamus River), the number of mature individuals increased by an estimated 78% over three generations (Upper 95% CI = 710%, Lower 95% CI = -61%) with the probability of a 30% decline at 0.1 (Table 14, Figure 19a,b). Using the entire time series of data, the number of mature individuals increased by an estimated 2% (Upper 95% CI = 308%, Lower 95% CI = -74%) with the probability of a 30% decline at 0.27 (Table 14, Figure 19a,c).The Squamish River system is the largest contributor to overall abundance (Figure 19f). For estimated wild abundance, the corresponding trends are the same (Figure 19f). While the trends are stable from 2005 to 2018, spawning is thought to occur elsewhere in the northern area.

Harvest, smolt-to-adult survival, and stock productivity data are unavailable for this DU because there is no CWT indicator stock.

Table 14. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 19. DU18 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

A Threats Calculator was not completed for this DU. For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material.

Hatchery releases have occurred within this DU, and the genetic origin of the released fish was often from outside the DU. The SSC concluded that such releases represent a threat to the wild fish in the DU due to competition and genetic introgression.

Designatable Unit 20: East Vancouver Island, ocean, summer population

The average generation time for this DU is 3.5 years. These fish exhibit ocean-type life-history variants and summer run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 20. Map of DU20 - East Vancouver Island Ocean Summer.

This DU is a combination of three areas on Vancouver Island. The northernmost section includes the Tsolum River drainage and the Puntledge River drainage downstream of Comox Lake, both of which empty into Georgia Strait via Courtenay River. This section extends north-to-south from the headwaters of the Tsolum River to just north of Maple Lake. The section’s westernmost extent occurs at the lower end of Comox Lake and its easternmost extent occurs at the Courtenay River confluence (N: Lat. 49.81, Long. 125.19; S: Lat. 49.64, Long. 125.02; W: Lat. 49.64, Long. 125.10; E: Lat. 49.69, Long. 124.00). The smallest, middle section includes the drainage area around Nanaimo Lakes (N: Lat. 49.12, Long. 124.18; S: Lat. 49.06, Long. 124.18; W: Lat. 49.09, Long. 124.24; E: Lat. 49.09, Long. 124.13). The largest, southern section includes the Cowichan, Koksilah, and Chemainus River drainages. This section extends southeast from the Upper Shaw Creek Woodlands to Cobble Hill. The area’s westernmost extent occurs at upper Cowichan Lake and its easternmost extent spans from just northeast of Cobble Hill, to the Koksilah River’s confluence with Cowichan River at Cowichan Bay, and near Maple Bay, BC just east of Quamichan Lake (N: Lat. 49.02, Long. 124.44; S: Lat. 48.60, Long.123.76, W: Lat. 48.89, Long. 124.51, E: Lat. 48.70, Long. 123.60). The DU’s centroid is at Lat. 49.12, Long. 124.07, and its total area is 1727.05 km². DU20 contains a large proportion of island coastal mountain ridge.

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 311 km² based on a total known spawning run length of 156 km, or 1.55% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (21.4%), with urban development comprising 3.5%, agricultural / rural development 2.3%, and mining development 0.3% of the DU area. Road density in DU20 is 2.3 km/km² with an average of 0.8 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 18.4% of the DU’s riparian habitat and 15.3% of its forest cover is disturbed. The DU is not affected by Mountain Pine Beetle.

Abundance

This DU is comprised only of two enhanced sites, and both are considered persistent (Appendix 1). All spawners originate from streams with high levels of enhancement (Figure 21a). The estimated wild portion of the population has fluctuated around the 20% mark since the 1980s (Figure 21b). Hatchery releases began in 1971, increasing to a peak of over 2 million fish in 1988, declining to less than 500,000 fish in the late 1990s, peaking again at over 3 million fish in 2001, and then declining again to less than 500,000 in 2018 (Figure 21c). No hatchery releases are reported from outside the DU (Figure 21d). The hatchery influence on the wild population, as measured by the PNI, is high and variable (see Appendix 1).

Figure 21. DU20 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Fluctuations and trends

Based on data from two persistent sites (Puntledge River and Nanaimo River), the number of mature individuals over the last three generations decreased by an estimated
-51% (Upper 95% CI = 42%, Lower 95% CI = -83%) with the probability of a 30% decline at 0.76 (Table 15, Figure 22a,b). Using the entire time series of data, the number of mature individuals increased by an estimated 39% (Upper 95% CI = 177%, Lower 95% CI = -30%) with the probability of a 30% decline at 0.02 (Table 15, Figure 22a,c). The Puntledge River system has historically been the largest contributor to overall abundance, although it is sometimes surpassed by the Nanaimo River system (Figure 22f).

For estimated wild abundance only, the change in the number of mature individuals over the last three generations decreased by an estimated -41% (Upper 95% CI = 155%, Lower 95% CI = -86%) with the probability of a 30% decline at 0.6 (Table 15, Figure 23a,b). For the full time series, the corresponding trend is a change in the number of mature individuals by an estimated 60% (Upper 95% CI = 225%, Lower 95% CI = -22%) with the probability of a 30% decline at 0 (Table 15, Figure 23a,c). The relative contribution of the Puntledge River to the wild population has been less over time than its relative contribution to the population as a whole (Figure 22f, Figure 23f). The Nanaimo River is the largest contributor to the wild population. The contribution of fish from hatcheries confounds the determination of population trends. According to a consensus of expert opinion, fewer than 1000 wild spawners remain in this population. While DFO data indicate that the average number of mature individuals remaining in 2018 are 1012 and 191 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1), the SSC places the most confidence on the consensus of experts’ estimate of remaining mature wild fish.

The exploitation rate in this DU was high in the 1970s and 1980s (up to ~80%), declined in the 1990s and early 2000s to ~10%, then increased after the mid-2000s to ~40% in 2013 (Figure 22d). Smolt-to-adult survival declined since the mid-1970s, but remained relatively stable at an average rate of 0.6% since 1983 (Figure 22e). Stock productivity data are not available for this DU.

Table 15. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 22. DU20 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Figure 23. DU20 - Spawner abundance trends adjusted by average proportion of natural origin spawners, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. Chinook Salmon experts who participated in the IUCN Threats Calculator Workshop in February 2017 concluded that this DU should be assigned a threat impact of High (B). The most important threats specific to this DU are ecosystem modifications and drought. The COSEWIC Marine Fishes SSC during their 2019 Annual Meeting, updated this Threats Calculator, with the assistance of local DFO experts, paying special attention to new information on hatchery threats and the impacts of dams. The updated threat impacts remained High.

The northern portion of this DU contains summer-run Chinook Salmon in the Puntledge River, which is also the CWT indicator stock for this DU. These salmon have been impacted heavily by the construction of a hydroelectric facility built in 1955 consisting of the Comox Dam (storage) as well as a diversion dam on Puntledge River. These impacts led to escapement estimates of summer-run Puntledge River Chinook Salmon declining from an average of about 3,000 to below 600 in 1975 (Guimond 2008). The dam limits access to spawning, rearing, and overwintering habitat due to its footprint and operations, including flow and diversions. These development impacts likely exacerbated predation by Harbour Seals due to the channelization of the lower Puntledge River (BC Hydro 2011). Enhancement efforts including spawning channels, a fishway, and fishing closures and restrictions, allowed the population to recover to ~1,200 in the mid-1980s but it declined again in the 1990s (BC Hydro 2011b). DFO has stated that recovery of summer Chinook Salmon will be accomplished through restoration, fish culture, and predator management (e.g., Yurk and Trites 2000). Part of this population is under captive breeding. At 0.6%, smolt-to-adult survival is likely below replacement.

A large number of hatchery releases have occurred within this DU, and the genetic origin of the released fish is from within the DU. The SSC concluded that such releases represent a serious threat to the wild fish in the DU due to competition and genetic introgression.

Other less important threats include housing and urban development, fire and fire suppression, problematic native species, and climate change impacts (habitat shifting and alteration, temperature extremes, storms and flooding).

Threats Calculator spreadsheets are included with this report (see Appendix 2).

Designatable Unit 21: East Vancouver Island, ocean, fall population

The average generation time for this DU is 3.3 years, with the exception of Qualicum/Puntledge Chinook Salmon which have an average generation time of 3.6 years. Chinook in this DU exhibit ocean-type life-history variants and fall run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 24. Map of DU21 - East Vancouver Island Ocean Fall.

This DU is a combination of four sections on Vancouver Island, each containing several drainages into the Strait of Georgia. The northern section includes the Oyster River, Tsolum River, Comox River, Puntledge River, Trent River, Tsable River, and Cowie Creek drainages. The section extends south from Simms Creek in Campbell River to the Tsable Lake Woodlands. The westernmost extent occurs in the headwaters of the Oyster River just east of Buttle Lake and the easternmost extent occurs where Tsable River and Cowie Creek enter the Strait of Georgia (N: Lat. 50.05, Long. 125.26; S: Lat. 49.44, Long. 124.96; W: Lat. 49.76, Long. 125.55; E: Lat. 49.52, Long. 124.84). The large middle section runs south from Rosewall Creek and the Beaufort Range along the Strait of Georgia to Haslam Creek and Nanaimo River headwaters. The section’s westernmost extent occurs along the Beaufort Range to the north and its easternmost extent occurs near Cedar, BC and Nanaimo River Regional Park (N: Lat. 49.44, Long. 124.89; S: Lat. 48.95, Long. 124.01; W: Lat. 49.41, Long. 124.91; E: Lat. 49.11, Long. 123.85). The two sections in the south include the Prospect Lake drainage to the east (N: Lat. 48.56, Long. 123.45; S: Lat. 48.49, Long. 123.44; W: Lat. 48.52, Long. 123.48; E: Lat. 48.52, Long. 123.41), which empties into Brentwood Bay, and the Butchart, Lubbe, Goldstream, Jack and Mavis Lake drainages to the west, which empty into Finlayson Arm (N: Lat. 48.55, Long. 123.65; S: Lat. 48.42, Long. 123.58; W: Lat. 48.47, Long. 123.65; E: Lat. 48.45, Long. 123.52). The DU’s centroid is at Lat. 49.63, Long. 124.84 and its total area is 4727.02 km². Like DU20, DU21 contains a large proportion of island coastal mountain ridge.

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 531 km² based on a total known spawning run length of 266 km, or 2.64% of the known spawning length across all DUs.

This DU is a combination of four WSP conservation units, CK-21, CK-22, CK-25, and CK-27.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (25.7%), with urban development comprising 4.8%, agricultural / rural development 3.8%, and mining development 0.06% of the DU area. Road density in DU21 is 2.4 km/km² with an average of 0.8 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 25.1% of the DU’s riparian habitat and 16.9% of its forest cover is disturbed. The DU is not affected by Mountain Pine Beetle.

Abundance

This DU is comprised only of enhanced sites, with the proportion of estimated spawners considered of natural origin varying depending on the WSP conservation unit (Figure 25a,b, Figure 26a,b, Figure 27a,b, Figure 28a,b). A total of 24 sites exist within the four Conservation Units, and eight are considered persistent (Appendix 1). Of the years where sampling occurred, mature individuals originated from streams that had moderate to high levels of enhancement. For CK-21, using the pNOS adjustment method, the wild portion of the population is estimated at 100%, which is inconsistent with the conservation unit’s enhanced status and hatchery release data shown in (Figure 25c and Figure 25d). Given this contradiction, Figure 25b has been omitted. Hatchery releases increased from the mid-1960s, with the largest number of releases occurring in CK-27 (nearly 8 million in 2018 but peaking at nearly 15 million fish in 1990) (Figure 25c, Figure 26c, Figure 27c, and Figure 28c).

Figure 25. DU21 (CK-21) - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation. % pNOS Adjusted (panel (b)) cannot be calculated due to sample size limitations.

Figure 26. DU21 (CK-22) - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Figure 27. DU21 (CK-25) - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Figure 28. DU21 (CK - 27) - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Fluctuations and trends

Based on the last three generations of data across all four WSP conservation units combined, including eight persistent sites (see Figure 29f), the number of mature individuals increased by an estimated 99% (Upper 95% CI = 298%, Lower 95% CI = 1%) with zero probability of a 30% decline (Table 16, Figure 29a,b). Using the entire time series of data, the number of mature individuals decreased by an estimated -7% (Upper 95% CI = 50%, Lower 95% CI = -43%) with the probability of a 30% decline at 0.12 (Table 16, Figure 29a,c). The Cowichan, Puntledge and Qualicum river systems are the largest contributors to overall abundance (Figure 29f).

Averaged across all four WSP conservation units (CUs), the exploitation rate declined from ~80% in 1973 to ~40% in the early 1990s (Figure 29d). CU-averaged smolt-to-adult survival rates declined from a high of ~25% during the 1970s and remained relatively constant from the early 1990s to 1995, fluctuating between ~1% and ~0. 5% (Figure 29e). Stock productivity decreased from the mid-1980s to 1999, but increased from 2000 to 2008 to ~10 recruits per spawner per brood year (see 'Fluctuations and trends' in 'Format of Designatable Unit-Specific Chapters' section for estimation methods) (Figure 30).

Information is available to disaggregate hatchery and wild fish trends. For estimated wild abundance only, the number of mature individuals increased by an estimated 180% (Upper 95% CI = 411%, Lower 95% CI = 51%) with the probability of a 30% decline at 0 (Table 16, Figure 31a,b). For the full time series, the increase in the number of mature individuals is estimated to be 40% (Upper 95% CI = 155%, Lower 95% CI = -24%) with the probability of a 30% decline at 0.01 (Table 16, Figure 31a,c). The relative contribution of the Cowichan River to the wild population has been substantially higher over time than its relative contribution to the population as a whole and it is the largest contributor to the wild population followed by Englishman River. DFO data indicate that the average number of mature individuals remaining in 2018 are 29446 and 9551 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1).

Table 16. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 29. DU21 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Figure 30. DU21 Stock productivity calculated as the total number of adults (spawners and catch) produced by spawners from a brood year (BY) divided by the number of spawners in the brood year. Productivity data are only available for CK-22. This figure is updated from Brown et al. 2013.

Figure 31. DU21 - Spawner abundance trends adjusted by average proportion of natural origin spawners, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. Chinook Salmon experts who participated in the IUCN Threats Calculator Workshop in February 2017 concluded that this DU should be assigned a threat impact of High (B). The most important threats specific to this DU are ecosystem modifications and water management/use. The Cowichan River population is increasing. However, the Strait of Georgia ecosystem is more variable and vulnerable to threats than other areas. Domestic and industrial water use is high with uncertain effects. Loading of water bombers for fire suppression could also have an impact depending on timing. The COSEWIC Marine Fishes SSC during their 2019 Annual Meeting, updated this Threats Calculator, with the assistance of local DFO experts, paying special attention to new information on hatchery threats and the impacts of dams. The SSC noted that a large number of hatchery releases have occurred and continue within this DU, and the genetic origin of the released fish is sometimes from outside the DU. The SSC concluded that hatchery strays into the Cowichan River could represent a serious threat to the wild fish in the DU due to competition and genetic introgression. The updated threat impacts remained High.

Total exploitation has stabilized but at a relatively high rate (~50%). Riddell et al. (2013) note that sustainable harvest is strongly tied to stock productivity, which decreased from the mid-1980s to 2000, but increased over the eight years from 2000 to 2008 - an encouraging signal. However, over the full time horizon of available data (1973-2010), marine survival declined by 90% overall for this stock. Recent smolt-to-adult survival rates are likely below replacement.

Included in this DU is the Puntledge River fall-run Chinook Salmon (in CK-27). The abundance estimates for these stocks mirror those of the summer run stock (BC Hydro 2011b), with low abundances in the 1980s and 1990s.

Other less important threats include housing and urban development, fire and fire suppression, invasive non-native species (Brown Trout [Salmo trutta]), problematic native species (seals, sea lions, birds), and climate change impacts (habitat shifting and alteration, droughts, temperature extremes, storms and flooding).

Threats Calculator spreadsheets are included with this report (see Appendix 2).

Designatable Unit 22: South Coast - Southern Fjords, ocean, fall

The average generation time for this DU is 3.6 years. These fish exhibit ocean-type life-history variants and fall run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 32. Map of DU22 - South Coast - Southern Fjords Ocean Fall.

This DU is a combination of seven geographically separated sections. The tiny westernmost section is the drainage area for four small lakes emptying into Warner Bay of Seymour Inlet west of Hibbard Lake (lake and stream names unavailable in the BC Gazetteer). The largest of the six sections extends southeast from Neechantz Peak (northwest of Mount Philley) to Kwalate Creek’s outlet into Knight Inlet. This section’s westernmost extent occurs near Waump Creek’s outlet into Alison Sound and the easternmost extent occurs at the Sim River’s outlet into Wahshihlas Bay (N: Lat. 51.47, Long. 126.70; S: Lat. 50.79, Long. 125.69; W: Lat. 51.19, Long. 126.98; E: Lat. 51.03, Long. 125.61). The westernmost of the three middle sections includes the Fulmore River, Tuna River, Reed Creek, Heydon Creek, and Glendale Creek drainages. This section extends eastward from just south of Burnt Mountain to the Heydon Creek outlet into Loughborough Inlet (N: Lat. 50.64, Long. 125.87; S: Lat. 50.47, Long. 125.95; W: Lat. 50.55, Long. 126.15; E: Lat. 50.57, Long. 125.57). Moving northeast, the next major section contains the Stafford, Apple, and Phillips River, and Frazer and Mink Creek drainages emptying into Cooper Reach and Phillips Arm. This section extends southeast from the upper part of the Stafford River drainage to the headwaters of the Phillips River around Mount Gardner. The westernmost extent occurs in the Frazer Creek headwaters and the easternmost extent occurs in the northern portion of the Phillips River headwaters (N: Lat. 50.95, Long. 125.31; S: Lat. 50.54, Long. 125.18; W: Lat. 50.69, Long. 125.56; E: Lat. 50.71, Long. 125.03). A fifth tiny section occurs along Phillips Arm just south of the Phillips River outlet. Moving northward, the sixth section contains the Franklin River drainage, extending south from Mount Waddington to upper Smyth Creek. This section’s westernmost extent occurs at the Franklin River’s outlet into Knight Inlet and the easternmost portion is around Mount Munday and the Ice Valley Glacier (N: Lat. 51.40, Long. 125.35; S: Lat. 51.02, Long. 125.42; W: Lat. 51.08, Long. 125.57; E: Lat. 51.32, Long. 125.20). The final section contains the Teaquahan, Southgate and Orford River drainages, which empty into Bute Inlet. This section extends southwest from Boulanger Creek to Dupont Creek. The westernmost extent occurs at the Teaquahan River outlet into Waddington Harbour and the easternmost extent occurs at Boulanger Creek around Mount Marston and Mount Durham (N: Lat. 51.14, Long. 124.27; S: Lat. 50.53, Long. 124.83; W: Lat. 50.93, Long. 124.84; E: Lat. 51.11, Long. 124.18). The DU’s centroid is at Lat. 50.77, Long. 125.78 and its total area is 7263.07 km². Like DU20 and DU21, DU22 contains a large proportion of coastal mountain ridge.

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 619 km² based on a total known spawning length of 309 km, or 3.07% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (4.1%), with agricultural/rural development comprising 0.002% of the area. Road density in DU22 is 0.2km/km² with an average of 0.4 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 3.2% of the DU’s riparian habitat and 4.1% of its forest cover is disturbed. DU22 contains no urban development or mining development, and the area is not affected by Mountain Pine Beetle.

Abundance

This DU has both enhanced and wild sites (Figure 33a), and of 15 sites identified within the DU, three are considered persistent (Appendix 1). Survey coverage is incomplete over time (Appendix 1) making it difficult to comment on trends in abundance. Only the Phillips River system, which is considered highly enhanced, is now consistently surveyed. Hatchery releases have fluctuated between ~0-225,000 fish since the 1990s, and remained around 100,000 fish from 2016-2018 (Figure 33c). One hatchery release from outside the DU is reported in 2005 (4,000 fish) (Figure 33d).

Figure 33. DU22 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.^{Footnote 2}

Fluctuations and trends

Survey coverage is incomplete over time (Appendix 1) making it difficult to comment on trends in abundance. Limited information is available to disaggregate hatchery and wild fish trends. The trends in population abundance are difficult to interpret due to the past influence of hatchery releases and changes in survey methodology.

Based on the last three generations of data at one persistent site (Phillips River), the number of mature individuals increased by an estimated 718% (Upper 95% CI = 3000%, Lower 95% CI = 114%) with the probability of a 30% decline at 0 (Table 17, Figure 34a,b). Using the entire time series of data, the number of mature individuals increased by an estimated 2030% (Upper 95% CI = 6550%, Lower 95% CI = 594%) with the probability of a 30% decline at 0 (Table 17, Figure 34a,c). Note that there was a change in survey methodology for the Phillips River to a more precise method, and therefore more recent estimates are not comparable with those prior to 2012. Accordingly, the estimates of population abundance change shown in Table 17 should be viewed with an abundance of caution.

For estimated wild abundance only, the corresponding trend for the full time series is an increase in the number of mature individuals by an estimated 2055% (Upper 95% CI = 6548%, Lower 95% CI = 593%) with a probability of a 30% decline at 0 (Table 17). For the last three generations of data, the corresponding trends are the same. DFO data indicate that the average number of mature individuals remaining in 2018 are 1969 and 267 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1).

The exploitation rate in this DU rose from ~10% to ~30% between 2009 and 2013 (Figure 34d), and smolt-to-adult survival declined from ~10% to ~3% over the same period (Figure 34e). Stock productivity data are not available for this DU.

Table 17. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 34. DU22 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

A Threats Calculator was not completed for this DU. For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material.

Hatchery releases have occurred within this DU, and the genetic origin of the released fish is generally from within the DU. The SSC concluded that such releases represent a threat to the wild fish in the DU due to competition and genetic introgression.

Designatable Unit 23: East Vancouver Island, ocean, fall (EVI + SFj) population

The average generation time for this DU is 4.4 years. These fish exhibit ocean-type life-history variants and fall run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 35. Map of DU23 - East Vancouver Island Ocean Fall (EVI + SFj).

This DU extends southeast from Nahwitti River around Mount Waddington to Thelwood Creek around Mount Septimus, and runs along Johnstone Strait east to Campbell River. The southern end is located at Mount Septimus and Mount Rousseau, while the western end is located at Pinder Creek close to Pinder Peak (N: Lat. 50.85, Long. 128.00; S: Lat. 49.48, Long. 125.50; W: Lat. 50.09, Long. 125.18; E: Lat. 50.21, Long. 127.04). The DU’s centroid is at Lat. 50.37, Long. 126.21 and its total area is 7181.18 km². DU23 contains a large proportion of Vancouver Island’s coastal mountain ridge.

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 292 km² based on a total known spawning run length of 146 km, or 1.45% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (17.9%), with urban development comprising 0.3%, agricultural / rural development 0.3%, and mining development 0.09% of the DU area. Road density in DU23 is 1.4 km/km² with an average of 0.8 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 17.4% of the DU’s riparian habitat and 17.2% of its forest cover is disturbed. The DU is not affected by Mountain Pine Beetle.

Abundance

There are 18 sites within the DU, and of those, five are considered persistent (Appendix 1). A large proportion of this DU’s spawners originate from enhanced streams (Figure 36a), with the proportion of estimated natural origin fish averaging ~20% (except for a peak to ~55% in the mid-2010s) (Figure 36b). Hatchery releases increased since the 1970s, peaking at nearly 5 million fish, then levelling off to around 3 million releases per year (Figure 36c). No hatchery releases are reported from outside the DU (Figure 36d).

Figure 36. DU23 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Fluctuations and trends

Information is available to disaggregate hatchery and wild fish trends.

Based on the last three generations of data at five persistent sites, the number of mature individuals increased by an estimated 6% (Upper 95% CI = 80%, Lower 95% CI = -38%) with the probability of a 30% decline at 0.06 (Table 18, Figure 37a,b). Using the entire time series of data, the number of mature individuals declined by an estimated -38% (Upper 95% CI = -5%, Lower 95% CI = -59%) with the probability of a 30% decline at 0.72 (Table 18, Figure 37a,c). The Quinsam river system is the largest contributor to overall abundance.

For estimated wild abundance only, the number of mature individuals increased by an estimated 48% (Upper 95% CI = 201%, Lower 95% CI = -28%) with the probability of a 30% decline at 0.02 (Table 18, Figure 38a,b). For the full time series, the number of mature individuals increased by an estimated 85% (Upper 95% CI = 203%, Lower 95% CI = 13%) with the probability of a 30% decline at 0 (Table 18, Figure 38a,c). The relative contributions of the Campbell, Nimpkish and Salmon river systems to the wild population are historically higher over time than their relative contributions to the population as a whole, while the reverse is true for the Quinsam River system (Figure 37f and Figure 38f). The Nimpkish river system is historically the largest contributor to the wild population, followed by the Salmon and Quinsam River systems.

DFO data indicate that the average number of mature individuals remaining in 2018 are 8298 and 2133 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1).

Note that while pNOS adjusted abundance estimates shown in Figure 38 incorporate contributions from the Campbell River and Quinsam River systems that are likely representative, at present these two systems are treated as one site for brood stock but as two sites for releases and returns. As such, the proportion of natural-origin brood stock (pNOB) and the PNI estimates for Campbell River may be biased low because they do not account for brood stock from Quinsam (see ‘Sampling Effort and Methods’ to review pNOS adjustment methods).

The exploitation rate in this DU declined from a high of ~80% in the late 1970s and fluctuated between ~20% to 40% from the mid-1990s to 2012 (Figure 37d). Smolt-to-adult survival declined from a peak rate of nearly 10% in the 1970s and remained relatively stable at an average rate of 0.9% since 1989 (Figure 37e). Stock productivity data are not available for this DU.

Table 18. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 37. DU23 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Figure 38. DU23 - Spawner abundance trends adjusted by average proportion of natural origin spawners, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. Chinook Salmon experts who participated in the IUCN Threats Calculator Workshop in February 2017 concluded that this DU should be assigned a threat impact of High - Medium (B/C). The most important threat specific to this DU is dams and water management/use. Releases of water from reservoirs can impact spawning habitat. A large number of hatchery releases have occurred and continue within this DU, and the genetic origin of the released fish is from within the DU. The SSC concluded that such releases represent a serious threat to the wild fish in the DU due to competition and genetic introgression. In particular, the influence of hatchery origin spawners in the Quinsam River is high, and they are probably a threat for the wild population (DFO 2014).

The total exploitation rate has stabilized but at a high rate (~0.4). From 1973 to 2010, the smolt-to-adult survival rate declined by 90% for this DU.

Other less important threats include fire and fire suppression, ecosystem modifications, agricultural and forestry effluents, avalanches/landslides, and climate change impacts (habitat shifting and alteration, storms and flooding).

Threats Calculator spreadsheets are included with this report (see Appendix 2).

Designatable Unit 24: West Vancouver Island, ocean, fall (South) population

The average generation time for this DU is 4 years. These fish exhibit ocean-type life-history variants and fall run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 39. Map of DU24 - West Vancouver Island Ocean Fall (South).

The geographic location of this DU extends north at Sydney River near Pretty Girl Peak (Lat. 49.57, Long. 126.36), and it runs along the Clayoquot Canyon west to Klanawa River (Lat. 48.92, Long. 125.51). The southern end is located at Sooke River around Empress Mountain at Lat. 48.39, Long. 123.58, and the eastern end is located at Lanterman Creek around Mount Harmston (Lat. 49.52, Long. 125.07). The DU’s centroid is at Lat. 49.03, Long. 125.15 and its total area is 6785.59 km². Like DU23, DU24 contains a large proportion of the Vancouver Island coastal mountain ridge.

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 761 km² based on a total known spawning run length of 381 km, or 3.79% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (18.0%), with urban development comprising 0.9%, agricultural/rural development 0.4%, and mining development 0.1% of the DU’s area. Road density in DU24 is 1.2 km/km² with an average of 0.6 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 18.2% of the DU’s riparian habitat and 16.5% of its forest cover is disturbed. DU24 is not affected by Mountain Pine Beetle.

Abundance

There are 53 sites within this DU, and 14 are considered persistent (Appendix 1). A large proportion of this DU’s spawners originate from enhanced streams (Figure 40a), with the proportion of estimated natural origin fish averaging <20% (Figure 40b). Hatchery releases increased to a peak of nearly 20 million fish in 1990 then dropped over the next twenty years to about 12.5 million fish in 2018 (Figure 40c). No hatchery releases are reported from outside the DU (Figure 40d).

Figure 40. DU24 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Fluctuations and trends

Available indices of abundance over the most recent three generations and over all years show conflicting trends that are difficult to reconcile. Based on the last three generations of data at fourteen persistent sites, the number of mature individuals increased by an estimated 83% (Upper 95% CI = 163%, Lower 95% CI = 28%) with the probability of a 30% decline at 0 (Table 19, Figure 41a,b). Using the entire time series of data, the number of mature individuals decreased by an estimated -14% (Upper 95% CI = 49%, Lower 95% CI = -49%) with the probability of a 30% decline at 0.21 (Table 19, Figure 41a,c). The Somass-Sproat and Nitinat river systems are the largest contributors to overall abundance.

For estimated wild abundance only, the number of mature individuals increased by an estimated 43% (Upper 95% CI = 129%, Lower 95% CI = -10%) with the probability of a 30% decline at 0 (Table 19, Figure 42a,b). For the entire time series of data, the number of mature individuals declined by an estimated -19% (Upper 95% CI = 24%, Lower 95% CI = -47%). With the exception of the Somass-Sproat, Nitinat, and Sarita river systems, the relative contributions of most sites to the wild population are historically higher than their relative contributions to the population as a whole, but the Somass-Sproat river system remains the largest contributor to the wild population.

Based on a consensus of expert opinion, fewer than 10,000 wild adults are thought to remain. While DFO data indicate that the average number of mature individuals remaining in 2018 are 53036 and 6365 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1), the SSC places the most confidence on the consensus of experts’ estimate of remaining mature wild fish.

The total exploitation rate (ER) dropped fairly steadily from a high of ~80% in 1973 to ~25% in the mid-1990s before fluctuating between ~25% to 60% through to 2014 (Figure 41d). Note that the terminal ER for this DU reflects the enhanced Robertson Creek hatchery component - wild fish from watersheds elsewhere in the DU have a lower ER (W. Luedke, pers. comm., 2019). Disaggregated ocean and terminal ERs are shown in Figure 43. Additionally, results from incomplete broods need to be interpreted cautiously.

Smolt-to-adult survival declined since the 1970s when it peaked at ~20% (Figure 41e). From the early 1990s to 2013, the rate fluctuated from ~0.03% to ~10%. Stock productivity data are not available for this DU.

Table 19. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 41. DU24 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation). Note that this figure shows incomplete exploitation rate data for the most recent cohorts.

Figure 42. DU24 - Spawner abundance trends adjusted by average proportion of natural origin spawners, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Figure 43. DU24 - Disaggregated ocean and terminal exploitation rates 1970-2015. Note that there are incomplete broods in 2014 and 2015, and the exploitation rates should be interpreted cautiously.

Threats and limiting factors

For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. Chinook Salmon experts who participated in the IUCN Threats Calculator Workshop in February 2017 concluded that this DU should be assigned a threat impact of High (B). The most important threats specific to this DU are ecosystem modifications, and agricultural and forestry effluents. The COSEWIC Marine Fishes SSC updated this Threats Calculator during their 2019 Annual Meeting, with the assistance of local DFO experts, paying special attention to new information on hatchery threats and the impacts of dams. A large number of hatchery releases have occurred and continue within this DU, and the genetic origin of the released fish is from within the DU. The SSC concluded that such releases represent a serious threat to the wild fish in the DU due to competition and genetic introgression. It was noted that straying of hatchery-origin spawners has been documented throughout the DU, supporting the view that the genetic composition of wild spawners and therefore the wildlife species are threatened by hatchery operations. The updated threat impacts was Very High- Very High (Appendix 2).

Other less important threats include tourism and recreation areas, industrial effluents, avalanches/landslides, and droughts, which are expected every other year and can delay adult returns due to low water levels.

Points of potential concern include the rate of increase in number of salmon farms in Clayoquot Sound, the large amount of tree farm licences (implying a high level of logging), and gravel aggradation (potential loss of spawning habitat with increased elevation due to the deposition of sediments).

Designatable Unit 25: West Vancouver Island, ocean, fall (Nootka and Kyuquot) population

The average generation time for this DU is 4 years. These fish exhibit ocean-type life-history variants and fall run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 44. Map of DU25 - West Vancouver Island Ocean Fall (Nootka and Kyuquot).

This DU extends south from Tahsish River around Merry Widow Mountain to Bancroft Creek around Mount Thelwood. The western extent stretches along the Esperanza Canyon to Tatchu Creek and the easternmost extent occurs at Gold River around Tyee Mountain (N: Lat. 50.34, Long. 127.09; S: Lat. 49.52, Long. 125.76; W: Lat. 49.89, Long. 127.17; E: Lat. 50.01, Long. 125.91). The DU’s centroid is at Lat. 49.91, Long. 126.85 and its total area is 3601.55km². DU25 contains a large proportion of Vancouver Island coastal mountain ridge.

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 375 km² based on a total known spawning run length of 187 km, or 1.86% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (13.1%), with urban development comprising 0.2%, and mining development 0.005% of the DU’s area. Road density in DU25 is 0.9 km/km² with an average of 0.8 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 13.8% of the DU’s riparian habitat and 12.9% of its forest cover is disturbed. No agricultural / rural development occurs within the DU and it is not affected by Mountain Pine Beetle.

Abundance

Spawner abundance data for most years originate from sites with moderate sampling effort/survey quality. However, a large portion of sites (29 out of 41) are considered by DFO to be data deficient (Appendix 1). At most of these sites, monitoring has stopped in recent years because of lack of natural spawning.

A large proportion of this DU’s spawners originate from enhanced streams (Figure 45a), with the proportion of estimated natural origin fish averaging ~20% (except in the 1980s) (Figure 45b). Of the years where sampling occurred, most individuals originated from streams that had moderate to high levels of enhancement. Hatchery releases increased from very low counts in the late 1970s to over 4 million fish in the mid-1990s before fluctuating between ~2 million and ~4 million fish up to 2018 (Figure 45c). No hatchery releases are reported from outside the DU (Figure 45d).

Figure 45. DU25 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation.

Fluctuations and trends

Available indices of abundance over the most recent three generations and over all years do not show declines. While this wildlife species spawns at a large number of sites, with survey information being available from many spawning areas, population trends are most likely heavily influenced by hatchery releases aimed to augment natural production.

Based on the last three generations of data at nine persistent sites (see Figure 46f), the number of mature individuals increased by an estimated 116% (Upper 95% CI = 654%, Lower 95% CI = -38%) with the probability of a 30% decline at 0.04 (Table 20). Using the entire time series of data, the number of mature individuals increased by an estimated 17% (Upper 95% CI = 151%, Lower 95% CI = -45%) with the probability of a 30% decline at 0.09 (Table 20, Figure 46a,c).The Conuma River system is the largest contributor to overall abundance (Figure 46f).

For estimated wild abundance only, the corresponding trend for the last three generations is an estimated 169% increase (Upper 95% CI = 473%, Lower 95% CI = 25%) with the probability of a 30% decline at 0 (Table 20, Figure 47a,b). For the full time series, there is an estimated 9% increase (Upper 95% CI = 107%, Lower 95% CI = -42%) with the probability of a 30% decline also at 0.08 (Table 20, Figure 47a,c). With the exception of the Conuma River system, the relative contributions of all sites to the wild population are historically higher than their relative contributions to the population as a whole (Figure 46f and Figure 47f). The Conuma and Gold river systems are the largest contributors to the wild population (Figure 47f).

A consensus of expert opinion indicated that the remaining number of spawners is less than the threshold (10,000), and only one subpopulation exists within the DU. There is a possibility that the number of mature individuals remaining is less than 2500, meeting the threshold for Endangered. While DFO data indicate that the average numbers of mature individuals remaining in 2018 are 35271 and 5568 for the non pNOS-adjusted and adjusted values, respectively (Appendix 1), the SSC places the most confidence on the consensus of experts’ estimate of remaining mature wild fish.

Harvest, smolt-to-adult survival and stock productivity data are unavailable for this DU because there is no CWT indicator stock.

Table 20. Summary of estimated rate of change (±95% credible interval) in spawner abundance and probability of decline (>30%, >50%, >70%) for the last three generations and the entire time series for both the full population and the estimated wild population.

Figure 46. DU25 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Figure 47. DU25 - Spawner abundance trends adjusted by average proportion of natural origin spawners, exploitation rate, marine (smolt-to-adult) survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material. Chinook Salmon experts who participated in the IUCN Threats Calculator Workshop in February 2017 concluded that this DU should be assigned a threat impact of Medium (C). The most important threat is from ecosystem modifications. Ongoing impacts include high flows due to deforestation that create various changes to habitat (e.g., temperature, sedimentation, food supply, large woody debris, movement of gravel to different parts of stream). Sediment management plans are being developed. The system is previously logged and has stabilized but could now be logged again. The COSEWIC Marine Fishes SSC updated this Threats Calculator during their 2019 Annual Meeting, with the assistance of local DFO experts, paying special attention to new information on hatchery threats and the impacts of dams. A large number of hatchery releases have occurred and continue within this DU, and the genetic origin of the released fish is from within the DU. The SSC concluded that such releases represent a serious threat to the wild fish in the DU due to competition and genetic introgression. Similar to DU 24, it was noted that straying of hatchery-origin spawners has been documented throughout the DU, likely compromising the genetic composition of wild spawners and therefore threatening the wildlife species. The updated threat impact has increased to High-Very High.

Although data are lacking, survival rates are thought to be declining for this DU.

Other less important threats include tourism/recreation areas (increase in fishing lodges to ~100 - these are located in areas important to Chinook Salmon rearing), industrial effluents (pulp mills are closed but effluent is still present), agriculture/forestry issues (aquaculture, herbicides/pesticides, siltation from forestry), avalanches/landslides, and droughts. Droughts are expected every other year and can delay adult returns due to low water levels.

Designatable Unit 26: West Vancouver Island, ocean, fall (WVI + WQCI) population

The average generation time for this DU is 4 years. These fish exhibit ocean-type life-history variants and fall run-timing.

To review methods pertaining to data reported within individual DU chapters, refer to the preliminary sections of this report.

Extent of occurrence and area of occupancy

Figure 48. Map of DU26 - West Vancouver Island Ocean Fall (WVI + WQCI).

Four geographically separated sections combine to form this DU. The northernmost section contains the Jensen Creek, Goodspeed River, and Denad Creek drainages and extends from Eric Lake in the northwest to the Goodspeed River drainage in the east and the Denad Creek outlet to Winter Harbour in the south (N: Lat. 50.76, Long. 128.01; S: Lat. 50.54, Long. 128.00; W: Lat. 50.70, Long. 128.29; E: Lat. 50.66, Long. 127.88). The two smaller sections further southeast contain the Wanokana Creek and Stephens Creek drainages, both of which empty into Holberg Inlet. The largest and southernmost section contains the Marble River, Mahatta Creek, Keith River, Klootchlimmis Creek, Klaskish River, and East Creek drainages. The section’s northernmost point occurs just northeast of Marble River Provincial Park and the southern point is at the headwaters of the Marble River. The DU extends from Keith River in the west to the Raging River around Mount Waddington in the east (N: Lat. 50.57, Long. 127.47; S: Lat. 50.23, Long. 127.30; W: Lat. 50.34, Long. 127.87; E: Lat. 50.35, Long. 127.08). The DU’s centroid is at Lat. 50.46, Long. 127.71 and its total area is 1307.62 km².

As for all DUs considered in this report, the Extent of Occurrence includes spawning streams as well as the ocean range, and is therefore >20,000 km². The IAO is 95 km² based on a total known spawning run length of 48 km, or 0.48% of the known spawning length across all DUs.

Habitat trends

Land surrounding this DU’s freshwater habitat is altered (18.5%), but with urban development comprising only 0.02% of the DU area. Road density in DU26 is 1.2 km/km² with an average of 0.9 stream crossings per km of fish accessible streams (the average across all DUs is 1.33 km/km² road density and 0.62 stream crossings per km of fish accessible streams). 17.7% of the DU’s riparian habitat and 18.4% of its forest cover is disturbed. No agricultural / rural or mining development currently occurs in this DU, although one mine was previously in operation near Coal Harbour and Rupert Inlet (M. Trudel, pers. comm., 2019). This DU is not affected by Mountain Pine Beetle.

Abundance

While spawning has been documented at a number of sites throughout this DU, survey information is available only for Marble River (Appendix 1). Information on the proportion of natural origin spawners is not available for this site. Given this, Figure 49b has been omitted. Hatchery releases increased from the mid-1980s to 2001, with a maximum release of ~1,000,000 in 2001. After 2001, the number of fish released declined to 2005 before increasing again to >800,000 fish by 2017 (Figure 49c). No hatchery releases are reported from outside the DU (Figure 49d).

Figure 49. DU26 - Enhancement, proportion of natural origin spawners, and hatchery releases. Graphics provided by Fisheries and Oceans Canada, see Table 4 for panel interpretation. % pNOS Adjusted (panel (b)) cannot be calculated.

Figure 50. DU26 - Spawner abundance trends, exploitation rate, smolt-to-adult survival, and percent site contribution to abundance (see Table 7 for panel interpretation).

Threats and limiting factors

A Threats Calculator was not completed for this DU. For general Threats and limiting factors applicable to all DUs, please refer to the Threats and limiting factors section in the introductory material.

Hatchery releases have occurred within this DU, and the genetic origin of the released fish is from within the DU. The SSC concluded that such releases represent a threat to the wild fish in the DU due to competition and genetic introgression.

Biographical summary of the report writers

Brian O. Ma (earlier report stages) is a Senior Systems Ecologist at ESSA Technologies Ltd. in Vancouver, BC. Previous to that he was an NSERC Postdoctoral Fellow with Fisheries and Oceans Canada where he worked as an ecological modeller for a high-profile sockeye salmon genomics project. Cedar Morton (later report stages) is a Senior Systems Ecologist at ESSA Technologies Ltd. in Vancouver BC. and holds a PhD from Simon Fraser University’s School of Resource and Environmental Management in Burnaby, BC. Diana Abraham (earlier report stages) is a researcher and science writer previously of ESSA Technologies Ltd., with over 20 years of experience. Aline Litt (later report stages) is a Research Assistant at ESSA Technologies Ltd. in Ottawa, ON and holds an MSc in Biology from Carleton University in Ottawa, ON.

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Appendix 1. Data quality and PNI trends by site for each designatable unit.

For each of the twelve DUs addressed in this Part Two report, this appendix provides a graphic for site-level data quality (all sites), and information on Proportionate Natural Influence (PNI) by site, where available.

Site-level data quality

Site-level data quality figures indicate the enhancement level (low (‘L’) or high (‘H’)) and the overall site type (persistent (‘P’) or data deficient (‘DD’)). Site type was determined using the process and criteria described in this report’s section entitled ‘Sampling Effort and Methods’. Data quality by year is described using the symbols defined in Figure 51.

Figure 51. Definitions for the symbols used in the site-level data quality figures provided for each of the DUs.

High quality escapement estimate

Moderate quality escapement estimate

Low quality escapement estimate

Unknown qualité escapement estimate

Gap fill

Other source

Merged Sites

High quality-Zero escapement

Logical error

Quality Filtered

PNI by site

The Proportionate Natural Influence metric is a measure of hatchery influence on the wild population. Site-specific PNI over time is shown when such data are available for each DU. Data origin is identified as either from ‘CWT’ for Coded-Wire Tag or ‘Thermal’ for thermal abundance data.

DU1

Figure 52 DU1 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

586 Campbell River ( High ) DU1 / CK−02 / Boundary Bay_FA_0.3

Figure 53. Campbell River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU6

Figure 54. DU6 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

DU13

Figure 55. DU13 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

46366 Eagle River ( Unk ) DU13 / CK−14 / South Thompson_SU_1.3

Figure 56. Eagle River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

46407 Salmon River ( High ) DU13 / CK−14 / South Thompson_SU_1.3

Figure 57. Salmon River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU15

Figure 58. DU15 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

46176 Nicola River ( Mod ) DU15 / CK−17 / Lower Thompson_SP_1.2

Figure 59. Nicola River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

46186 Spius Creek ( High ) DU15 / CK−17 / Lower Thompson_SP_1.2

Figure 60. Spius Creek PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

46196 Coldwater River ( High ) DU15 / CK−17 / Lower Thompson_SP_1.2

Figure 61. Coldwater River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

46206 Bonaparte River ( Low ) DU15 / CK−17 / Lower Thompson_SP_1.2

Figure 62. Bonaparte River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

46216 Deadman River ( Mod ) DU15 / CK−17 / Lower Thompson_SP_1.2

Figure 63. Deadman River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU18

Figure 64. DU18 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

DU20

Figure 65. DU20 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

51518 Nanaimo River ( High ) DU20 / CK−83 / East Vancouver Island−Georgia Strait_SU_0.3

Figure 66. Nanaimo River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

53068 Puntledge River ( High ) DU20 / CK−83 / East Vancouver Island−Georgia Strait_SU_0.3

Figure 67. Puntledge River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU21

Figure 68. DU21 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

Figure 69. DU21 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

Figure 70. DU21 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

Figure 71. DU21 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

39984 Chemainus River ( High ) DU21 / CK−25 / East Vancouver Island−Nanaimo and Chemainus_FA_0.x

Figure 72. Chemainus River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

40023 Cowichan River ( High ) DU21 / CK−22 / East Vancouver Island−Cowichan and Koksilah_FA_0.x

Figure 73. Cowichan River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

51368 Qualicum River ( High ) DU21 / CK−27 / East Vancouver Island−Qualicum and Puntledge_FA_0.x

Figure 74. Qualicum River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

51388 Little Qualicum River ( High ) DU21 / CK−27 / East Vancouver Island−Qualicum and Puntledge_FA_0.x

Figure 75. Little Qualicum River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

51519 Nanaimo River ( High ) DU21 / CK−25 / East Vancouver Island−Nanaimo and Chemainus_FA_0.x

Figure 76. Nanaimo River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

53069 Puntledge River ( High ) DU21 / CK−27 / East Vancouver Island−Qualicum and Puntledge_FA_0.x

Figure 77. Puntledge River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU22

Figure 78. DU22 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation. Note that upon more recent review, Fisheries and Oceans Canada consider Kingcome and Wakeman Rivers to be Data Deficient.

50618 Phillips River ( High ) DU22 / CK−28 / Southern Mainland−Southern Fjords_FA_0.x

Figure 79. Phillips River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU23

Figure 80. DU23 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

52718 Salmon River ( High ) DU23 / CK−29 / East Vancouver Island−North_FA_0.x

Figure 81. Salmon River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

52918 Campbell River ( High ) DU23 / CK−29 / East Vancouver Island−North_FA_0.x

Figure 82. Campbell River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

52948 Quinsam River ( High ) DU23 / CK−29 / East Vancouver Island−North_FA_0.x

Figure 83. Quinsam River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU24

Figure 84. DU24 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

3306 Somass−Sproat−Gc System ( High ) DU24 / CK−31 / West Vancouver Island−South_FA_0.x

Figure 85. Somass-Sproat-GC System PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

40153 Sooke River ( High ) DU24 / CK−31 / West Vancouver Island−South_FA_0.x

Figure 86. Sooke River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

40253 San Juan River ( High ) DU24 / CK−31 / West Vancouver Island−South_FA_0.x

Figure 87. San Juan River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

40363 Nitinat River ( High ) DU24 / CK−31 / West Vancouver Island−South_FA_0.x

Figure 88. Nitinat River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

40458 Sarita River ( High ) DU24 / CK−31 / West Vancouver Island−South_FA_0.x

Figure 89. Sarita River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

40618 Nahmint River ( High ) DU24 / CK−31 / West Vancouver Island−South_FA_0.x

Figure 90. Nahmint River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

45190 Bedwell System ( Mod ) DU24 / CK−31 / West Vancouver Island−South_FA_0.x

Figure 91. Bedwell River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU25

Figure 92. DU25 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

41328 Burman River ( High ) DU25 / CK−32 / West Vancouver Island−Nootka and Kyuquot_FA_0.x

Figure 93. Burman River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

41438 Conuma River ( High ) DU25 / CK−32 / West Vancouver Island−Nootka and Kyuquot_FA_0.x

Figure 94. Conuma River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

41498 Leiner River ( Mod ) DU25 / CK−32 / West Vancouver Island−Nootka and Kyuquot_FA_0.x

Figure 95. Leiner River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

41518 Tahsis River ( High ) DU25 / CK−32 / West Vancouver Island−Nootka and Kyuquot_FA_0.x

Figure 96. Tahsis River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

41713 Zeballos River ( High ) DU25 / CK−32 / West Vancouver Island−Nootka and Kyuquot_FA_0.x

Figure 97. Zeballos River PNI over time. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘PNI by site’ for interpretation.

DU26

Figure 98. DU26 - Data quality by site. Graphics provided by Fisheries and Oceans Canada, see Appendix 1 Section ‘Site-level data quality’ for interpretation.

Appendix 2. Threats calculators

Threats assessment worksheet - DU15

Species or ecosystem scientific name

Oncorhynchus tshawytscha - Chinook Salmon

Element ID

DU15 -Lower Thompson Stream Spring

Date:

11/6/2014

Assessor(s):

Brian O. Ma; modified 2/22/2017 in COSEWIC IUCN Threats Calculator workshop with Nicole Trouton, Greg Wilson, Jeff Grout, Cedar Morton, Carolyn Churchland, Richard Bailey, Marla Maxwell

References:

(Porter et al. 2013; Riddell et al. 2013; Brown et al. 2013, Pre-COSEWIC report, in-prep)

Overall threat impact calculation help:

Level 1 Threat Impact Counts

Assigned overall threat impact:

BC = High - Medium

Overall threat comments

Generation time = just under 4yrs. The most important impacts in this DU are from ecosystem modifications (poor ocean survival from El Nino; groundwater/runoff mix and shifting timing/volume of snowmelt). Harvest rate has increased while marine survival rate has declined. However, Riddell et al. (2013) note that sustainable harvest is strongly tied to stock productivity, and this DU does not have a reliable estimate of stock productivity. Other less challenging impacts include: invasive species, avalanches/landslides, droughts and temperature extremes.

Threats assessment worksheet - DU20

Species or ecosystem scientific name

Oncorhynchus tshawytscha - Chinook Salmon

Element ID

DU20 BC East Vancouver Island Ocean summer

Date:

2/22/21

Assessor(s):

Originally assessed by Brian O. Ma in November, 2014. Revised in February 2017 workshop by Wilf Luedke, Steve Baillie, Arlene Tompkins, Jason Mahoney, Cheryl Lynch, John Neilson (Marine Fishes SSC Co-chair), David Fraser (Facilitator), Bev McBride (COSEWIC Secretariat). Updated August 2019 by the Marine Fishes SSC and DFO Expert Observers.

References:

(Porter et al. 2013; Riddell et al. 2013; Brown et al. 2013, Pre-COSEWIC report, in-prep)

Overall threat impact calculation help:

Level 1 Threat Impact Counts

Assigned overall threat impact:

B = High

Overall threat comments

Generation Time 3.5 years. There is some uncertainty in the status of the Cowichan R. summer run so these comments pertain to Nanaimo River (several 100) and Puntledge River (approx 1000) only. Part of population is under captive breeding.