MARINE MAMMAL COMMISSION - Annual Report for 1998 



54,300 porpoises (95 percent confidence interval 

 41,300 to 71,400). 



A direct measure of population trends is not 

 possible because no regionwide harbor porpoise 

 surveys have been conducted before 1991 or since 

 1995 (another survey is scheduled for the summer of 

 1999). However, using information on harbor por- 

 poise life history, population size, and incidental take 

 levels, the National Marine Fisheries Service conclud- 

 ed early in the 1990s that the number of harbor 

 porpoises being caught in gillnets was probably 

 exceeding sustainable levels for the stock. 



Reliable estimates of harbor porpoise bycatch 

 levels were not available in the 1980s. Because of 

 growing concern about the possible effects on the 

 regional harbor porpoise stock, the National Marine 

 Fisheries Service began a program in 1989 to place 

 observers aboard a representative sample of gillnet 

 boats fishing in coastal waters of the Gulf of Maine to 

 assess incidental take rates. By expanding the ob- 

 served bycatch rates with a measure of total gillnet 

 fishing effort for the Gulf of Maine, the Service was 

 able to estimate bycatch levels for the area. A similar 

 observer program began in Canada in the Bay of 

 Fundy in 1994. As information on gillnet fishing and 

 the resulting incidental take of harbor porpoises 

 became available for other areas off New England and 

 along U.S. mid- Atlantic coastal states, observer 

 efforts were initiated and bycatch estimates were 

 developed for those areas as well (Table 3). 



Most gillnet fishing involving the incidental take of 

 Gulf of Maine harbor porpoises in U.S. and Canadian 

 waters is now sampled by observers. However, there 

 are no bycatch estimates for fishing in the Bay of 

 Fundy before 1993 and no estimates for the mid- 

 Atlantic region before 1995. Thus, for recent years, 

 the sum of the three regional bycatch estimates 

 provides a relatively complete reflection of overall 

 bycatch from the stock, but earlier estimates omit 

 substantial amounts of bycatch. 



As shown in Table 3, bycatch estimates for the 

 Gulf of Maine and the Bay of Fundy appear to have 

 declined substantially since 1993, including a decline 

 of about 50 percent between 1994 and 1997. This is 

 due, at least in part, to management actions designed 



to reduce gillnet fishing effort and protect harbor 

 porpoises. The decline since 1993 includes a sharp 

 drop in bycatch levels in Canada, which appears to be 

 due to a substantial decrease in overall fishing effort. 

 However, the establishment of time-area fishing 

 closures and the use of pingers in Canadian waters 

 also may have contributed partially to the reduced 

 catch in this area. Bycatch data for U.S. waters also 

 indicate that, in areas where past bycatch levels have 

 been high and extensive time-area fishing closures 

 established {e.g., coastal waters between northeastern 

 Massachusetts and southern Maine), bycatch levels 

 have declined substantially. These decreases, howev- 

 er, have been offset by increases in bycatch in other 

 areas, such as inshore waters south of Cape Cod and 

 offshore waters in the southern Gulf of Maine, where 

 fishing effort has expanded and time-area management 

 efforts have been absent or limited in scope. 



The recent increase in bycatch estimates off U.S. 

 mid-Atlantic coastal states, from about 100 in 1995 to 

 about 570 in 1997, also is a significant factor in why 

 the total bycatch estimates for all areas have declined 

 little. The increase in this area could correspond to 

 expansion in the mid-Atlantic area observer program, 

 increased fishing effort, or both. For the most part, 

 the increase in bycatch estimates for this area proba- 

 bly reflects a more complete and accurate regional 

 estimate, rather than an actual fivefold increase in the 

 incidental take levels. 



Management Actions before 1998 



In October 1992 the National Marine Fisheries 

 Service asked the New England Fisheries Management 

 Council to amend the northeast multi-species fishery 

 management plan under which the New England sink 

 gillnet fisheries for groundfish are managed. Specifi- 

 cally, it asked the Council to include an objective in 

 the plan for reducing harbor porpoise bycatch. 

 Pursuant to this request, the Council began recom- 

 mending management measures to reduce harbor por- 

 poise bycatch off New England. The first of these, 

 implemented by the National Marine Fisheries Service 

 in 1994, established seasonal time-area fishing clo- 

 sures in areas of high bycatch. They proved to be too 

 brief and too narrowly drawn to be effective and, 

 since then, the time period, size, and number of 

 closures have gradually been increased. 



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