Chapter III — Species of Special Concern 



ings and asking for advice as to whether and how 

 acoustic alarms might be incorporated into future 

 management decisions for the regional sink gillnet 

 fishery. The Commission, in consultation with its 

 Committee of Scientific Advisors, reviewed the report 

 and replied to the Council on 14 August 1995. 



The draft report noted that during the study 421 

 sets were made with inactive alarms and 423 sets with 

 active alarms. It also reported that only two porpoises 

 were caught in nets with active alarms, while 25 

 porpoises (0.059 porpoise per set) were caught in nets 

 with inactive alarms. Most of the porpoises caught 

 were mature males. Three harbor seals were also 

 caught — two in nets with active alarms and one in a 

 net with inactive alarms. Among other things, the 

 investigators noted that it was not clear why the 

 alarms had worked so well or whether animals would 

 habituate to the sound over time, rendering the alarms 

 ineffective. They also cautioned that the results 

 should not be extrapolated to other porpoise or 

 dolphin species. They concluded, however, that 

 acoustic alarms would be an effective means of 

 reducing the incidental catch of harbor porpoises in 

 the sink gillnet fishery in the Gulf of Maine. 



In its 14 August letter, the Commission noted that 

 the study design was well conceived, the statistical 

 methods used to analyze the data were appropriate, 

 and the results were very encouraging and highly 

 significant. However, given uncertainties (such as 

 potential habituation of porpoises to deterrent sound 

 and possible differences in the effectiveness of deter- 

 rents in areas and seasons where the age-sex composi- 

 tion, social interactions, and behavior of porpoises 

 could differ from those in the study) the Commission 

 noted there was a clear need for further study of the 

 device's effectiveness. Therefore, pending further 

 study, the Commission cautioned against relying on 

 the use of acoustic deterrents in normal fishing 

 practices to reduce harbor porpoise bycatch. 



With regard to incorporating use of the devices 

 into future management actions, the Commission 

 noted that the Service had recently adopted a system 

 of three time-area closures recommended by the 

 Council to reduce harbor porpoise bycatch. Based on 

 past observer data, however, the closures covered 

 only part of the peak bycatch areas and time periods 



(see below). The Commission therefore recommend- 

 ed that the seasonal closures be expanded to better 

 bracket the months and areas where past observer data 

 indicated high porpoise bycatch had occurred, and that 

 limited fishing opportunities be allowed within those 

 closures to further test the effectiveness of acoustic 

 deterrents, preferably by using the same methodology 

 as in the 1994 study. 



The Northeast Multispecies Fishery 



In 1986 the National Marine Fisheries Service 

 adopted a fishery management plan prepared by New 

 England Fishery Management Council to manage the 

 fishery for groundfish (e.g., cod, flounder, and 

 haddock) taken off New England by trawls, longlines, 

 and sink gillnets. Because of the large harbor por- 

 poise bycatch, in October 1992 the Service asked the 

 Council to develop an amendment to that plan to 

 reduce the incidental take of porpoise in the sink 

 gillnet component of the fishery. The Council in turn 

 established a harbor porpoise subgroup to analyze 

 porpoise bycatch patterns using data from the Ser- 

 vice's fishery observer program for the 1991 and 

 1992 fishing seasons. 



The analysis indicated that the bycatch of harbor 

 porpoises shifted by season and area as harbor por- 

 poise migrated along the coast. Depending on the 

 year, about one-half to three-fourths of the bycatch 

 occurred in a "mid-coast" area between northeast 

 Massachusetts and southern Maine, particularly 

 around a topographic feature called Jeffreys Ledge, 

 from October to December, and along a "northeast" 

 area off the central and northern coast of Maine from 

 June to September. Lower bycatch levels also oc- 

 curred in the mid-coast area in April and May, and a 

 few porpoises also were caught in Massachusetts Bay 

 in March and April. 



Based on this information, in September 1993 the 

 Council recommended interim take-reduction measures 

 on which the National Marine Fisheries Service 

 requested public comments in October. The Council 

 proposed adding a goal to the fishery management 

 plan to reduce harbor porpoise bycatch levels by 20 

 percent per year over a four-year period to reach an 

 annual bycatch level of less than two percent of the 

 stock's estimated size by the fifth year. Assuming a 



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