Harbour porpoise (Northwest Atlantic population) COSEWIC assessment and status report: chapter 13

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Existing protection or other status designations

Management of the harbour porpoise and other marine mammals falls under the Marine Mammal Regulations (SOR/93-56) of the Fisheries Act of Canada. These regulations do not, however, have any provisions to address the bycatch of marine mammals in commercial fisheries, the primary threat to harbour porpoises in eastern Canada. Experiments have been conducted in the Bay of Fundy to develop mitigation measures, such as the use of acoustic alarms, or pingers (Trippel et al. 1999; Cox et al. 2001) and acoustically modified gillnets (Trippel et al. 2003). To date, however, none of these measures has been implemented in any gillnet fishery in eastern Canada. The primary protective measures for harbour porpoises in eastern Canada are limitations on gillnet fishing effort designed to conserve groundfish stocks in the Bay of Fundy, Gulf of St. Lawrence and Newfoundland.

In October 1994, the Department of Fisheries and Oceans (DFO) released a Draft Harbour Porpoise Conservation Plan for the Bay of Fundy. The intent of this plan was to “assist the present population of harbour porpoises in the Bay of Fundy/Gulf of Maine to grow to a level where the occasional take by fishing operations will not seriously influence the sustainability of the population.” To achieve this goal, several measures were to be taken, including holding consultations with the fishing industry and U.S. regulatory agencies. The Plan sets a cap of 110 harbour porpoises per year from the Canadian portion of its range (i.e., the Bay of Fundy). Implementation of the Plan by DFO involved within-season monitoring of porpoise bycatch (through an independent bycatch program) and commercial fishing effort data (gillnet vessel day trips). Fishermen were instructed through annual pre-season consultative meetings that if the bycatch was expected to exceed 110 animals the fishery would be closed for the remainder of the season. The final DFO Harbour Porpoise Conservation Strategy for the Bay of Fundy was signed by the Regional Director General (Maritimes Region) in November 1995. Reviewers of the current document have indicated that this strategy is still in place.

The range of the harbour porpoises in eastern Canada extends into the United States, where the species is protected under the Marine Mammal Protection Act (MMPA) of 1972. The maximum allowable annual removal limit for each stock of marine mammals in the U.S. is referred to as the potential biological removal level (PBR) (Wade 1998b; Read and Wade 2001). The current PBR for harbour porpoises in the Bay of Fundy and Gulf of Maine is 747 (Waring et al. 2001). Marine mammal stocks for which anthropogenic mortality exceeds PBR are designated as strategic. Once a stock is declared strategic, management actions must be formulated to reduce levels of mortality and serious injury to below PBR. Typically, a Take Reduction Team is formed to address situations in which bycatches exceed PBR. These Teams are composed of representatives of stakeholder groups, including fishermen, scientists, conservation groups and managers, who negotiate a plan to reduce the magnitude of anthropogenic mortality to below PBR within a specified period (see Bache (2001) and Young (2001) for a more detailed description).

Two Take Reduction Teams (TRTs) have been formed in the United States to address the bycatch of harbour porpoises from the Bay of Fundy-Gulf of Maine subpopulation in commercial fisheries: the Gulf of Maine Harbour Porpoise TRT (formed in February 1996) and the Mid-Atlantic Harbour Porpoise TRT (formed in February 1997). Both teams recommended measures to reduce the bycatches of harbour porpoises in commercial fisheries. These measures were published together as the Harbor Porpoise Take Reduction Plan Regulations by the National Marine Fisheries Service (NMFS) in December 1998 (see http://www.nero.nmfs.gov/porptrp/). These regulations combine a complex mix of measures, including: times and areas completely closed to gillnet fishing for groundfish; times and areas in which acoustic alarms (or ‘pingers’) are required on groundfish gillnets (Kraus et al. 1997); and a series of required modifications to the structure and use of groundfish gillnets.

It is clear (Table 3) that harbour porpoise bycatches were decreasing for some time prior to the implementation of these regulations in 1998. Part of this reduction was due to conservation measures designed to reduce porpoise bycatches implemented by the New England Fisheries Management Council as early as 1994. These measures included closures to all groundfish gillnet fishing in certain parts of the Gulf of Maine (Murray et al. 2000). During this period, significant changes were occurring in the gillnet fishery because of fisheries management measures designed to conserve depleted stocks of groundfish in the Gulf of Maine and Mid-Atlantic states. 

In January, 1993 NMFS proposed listing the harbour porpoise subpopulation in the Bay of Fundy-Gulf of Maine as a threatened species under the United States Endangered Species Act (NMFS 1993). This listing was proposed because inadequate regulatory measures existed in Canada and the United States to address the bycatches of harbour porpoises in commercial fisheries. Action on this proposal was deferred for several years as the New England Fisheries Management Council and the two Take Reduction Teams developed strategies to reduce the bycatch of porpoises in gillnet fisheries. In January 1999, NMFS determined that the proposed listing was not warranted because the bycatch reduction programs implemented in Canada and the United States were sufficient to reverse any decline in abundance and ensure that removals were sustainable (NMFS 1999). As part of this determination, Wade (1998a) conducted a Population Viability Analysis (PVA) of the Bay of Fundy-Gulf of Maine harbour porpoise subpopulation. Using abundance data from 1991-1995 and bycatch data from 1992-1996 (see Tables table2 and table3), Wade estimated a low overall probability of extinction in 20 years (<0.005), but a high (0.28-0.72) overall probability of extinction within 100 years. Reducing the bycatch to one-quarter of the 1992-1996 levels eliminated the risk of extinction within 20 years and made the overall risk of extinction within 100 years very low (0.00-0.01). The 1999 estimate of abundance was considerably larger than the 1991-1995 estimates (Table 2) and bycatches in 1999 were less than one-quarter of the mean value from 1992-1996 (Table 3). In August 2001, NMFS published its intention to remove this subpopulation from the candidate list under the Endangered Species Act (NMFS 2001).

The harbour porpoise is classified as Vulnerable in the IUCN Red List due to suspected reductions in its extent of occurrence and quality of habitat, and because of high levels of bycatch throughout much of its range (The IUCN Red List of Threatened Species).