MARINE MAMMAL COMMISSION — Annual Report for 1991 



net fisheries for halibut and other finfish. In the 

 northwest Atlantic, an estimated 300 to 1,500 harbor 

 porpoises are killed each year in the groundfish gillnet 

 fishery. Until 1991, the total estimated harbor 

 porpoise population in the northwest Atlantic was 

 approximately 23,000 animals. A recent survey by 

 the National Marine Fisheries Service's Northeast 

 Fisheries Science Center, discussed below, has led to 

 a revised estimate. 



The number, size, discreteness, and productivity of 

 harbor porpoise populations in U.S. waters has not 

 been documented, and it is difficult to judge whether 

 the level of take has caused or is causing one or more 

 populations to be reduced below the maximum net 

 productivity level. As noted in past Annual Reports, 

 in 1986 and 1987 the Marine Mammal Commission 

 provided funds to the University of California at Santa 

 Cruz for a pilot project to radio-tag and track harbor 

 porpoises. The purpose of the study was to obtain 

 information on distribution and movement to help 

 assess the relative discreteness of harbor porpoise 

 populations off the west coast of the United States. 

 The investigators were unable to catch animals, and 

 the research objectives were not met (see Appendix B, 

 SilhQTetal. 1990). 



On 8 August 1990, a group of scientists and 

 conservationists in New England wrote to the Marine 

 Mammal Commission to express concern about the 

 status of harbor porpoises in the Gulf of Maine. In 

 the letter, the group noted that a 1981 survey carried 

 out by the New England Aquarium with support from 

 the National Marine Fisheries Service indicated that 

 between 8,000 and 15,300 harbor porpoises were 

 present in U.S. coastal waters in the Gulf of Maine. 

 Based on mortality estimates from various sources, the 

 group estimated that 1,000 harbor porpoises are 

 caught and killed each year in the Gulf of Maine and 

 Bay of Fundy fisheries. The group also noted that 

 studies comparing animals caught in the late 1970s 

 with those taken in 1987 and 1988 indicate a change 

 in population age structure that is characteristic of a 

 declining population. 



Based on this information, the group concluded 

 that the harbor porpoise population in the Gulf of 

 Maine is in trouble. It sought the Commission's 

 support for a number of recommended actions aimed 



at conserving the population. Among other things, 

 the group recommended: (1) listing the harbor 

 porpoise as threatened or endangered under the 

 Endangered Species Act (the species is already listed 

 as threatened by the Canadian Government's Com- 

 mittee on the Status of Endangered Wildlife); (2) 

 repeating the 1982 Gulf of Maine harbor porpoise 

 survey to determine current abundance; (3) analyzing 

 harbor porpoise sighting data collected over the past 

 decade to detect possible trends in relative abundance; 

 (4) closing certain areas to gillnet fishing on a season- | 

 al basis, if necessary, to protect and rebuild the 

 harbor porpoise population; and (5) investigating ways 

 to reduce the incidental take of harbor porpoises in 

 fishing nets. 



The Commission, in consultation with its Com- 

 mittee of Scientific Advisors, reviewed the letter and, 

 on 10 October 1990, advised the National Marine 

 Fisheries Service that it agreed that there is reason to 

 believe that incidental taking may be having a signifi- 

 cant adverse effect on harbor porpoise populations in 

 the northwest Atlantic. The Commission further 

 noted that incidental take in commercial fisheries also 

 may be having a significant adverse effect on harbor 

 porpoises off central California and possibly off 

 Washington and Alaska. 



In its letter, the Commission requested, among 

 other things, that the Service advise it of the results of 

 the fishery observer programs and population assess- 

 ment programs conducted by the Service's Northeast 

 and Southwest Fisheries Science Centers as they 

 pertain to harbor porpoises, and what the Service was 

 doing or planned to do to assess and monitor the 

 status of affected harbor porpoise populations in the 

 northwest Atlantic and along the west coast of the 

 United States. The Commission also noted that 

 effective conservation of harbor porpoise populations 

 would require cooperative efforts with Canada. 

 Therefore, the Commission recommended that, if the 

 Service had not already done so, it consult with the 

 responsible Canadian authorities to develop a coordi- 

 nated harbor porpoise research and management 

 program. 



The National Marine Fisheries Service responded 

 to the Commission's letter on 6 February 1991 . In its 

 letter, the Service agreed that more detailed informa- 



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