. . . Atlantic Marine Mammals 



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ISSUES 



Three issues of particular concern are: 1) 

 Have fisheries interactions and other 

 human-related activities significantly al- 

 tered the carrying capacity of the marine 

 ecosystem or directly affected marine 

 mammal populations, 2) are the depleted 



marine mammal species recovering and 

 have appropriate measures been taken to 

 facilitate recovery, and 3) what is the sig- 

 nificance of the recent mass strandings of 

 marine mammals? 



Fisheries and 

 Ecosystem Interactions 



Information on the incidental take of ma- 

 rine mammals in commercial fisheries is 

 incomplete; a fishery-wide observer pro- 

 gram was started in 1989, however. Be- 

 sides the potential impacts of incidental 

 marine mammal take, an assessment of 

 the effect of fisheries and other human 

 activities on the ecosystem is a critical 

 long-term concern that requires more re- 

 search. Meeting the 1988 amendments to 

 the MMPA is an important first step in that 

 process. 



Bottlenose dolphins in the Gulf of Mexico 

 are captured alive for use at public dis- 

 plays; additional animals are lost to com- 

 mercial fishing operations and illegal 

 shooting. The number of these losses is 

 poorly known, though estimates run to 

 more than 1% of the stock yearly. Pilot 

 whales are sometimes killed in foreign and 

 (J.S. mackerel and swordfish drift gillnet 

 fisheries off New England. Some white- 

 sided dolphins, bottlenose dolphins, 

 striped dolphins, and beaked whales may 

 also be killed in these fisheries. The impact 

 of this loss is unknown, but much of it has 

 recently included pregnant and nursing fe- 

 males. 



The incidental take of harbor porpoise in 

 the Gulf of Maine groundfish gillnet fishery 

 was estimated at 60-1,000 per year over 

 the past decade; the larger takes probably 

 have a significant impact on the popula- 

 tion. Canadian studies found that inciden- 

 tal takes caused a shift toward smaller and 

 younger animals in the population. 



Direct interactions between fin whales 

 and commercial fisheries are infrequent 

 and usually not fatal. Recent studies sug- 

 gest, however, that fin whales often feed on 

 commercially valuable pelagic fishes. 

 Humpback whales have been caught in a 

 wide variety of fishing gear. From 1975 to 

 1990, 51 humpbacks were reported en- 

 tangled (20-25% died, though most were 

 released alive). Another 450 humpbacks 

 became entangled in gear in Canadian 

 waters during the same time period. Har- 

 bor seals are incidentally taken in several 

 Gulf of Maine fisheries, particularly in 

 groundfish gill nets, but the impact of the 

 take is not known. Current levels of such 

 losses are probably small. Harbor seals 

 also steal lobster pot bait and eat pen- 

 raised salmon. 



Recovery of 

 Protected Species 



Six U.S. Atlantic coast marine mammals 

 are listed as endangered under the ESA. 

 Although data are incomplete, only the 

 right whale appears at such a critically low 

 level that its long-term survival is in ques- 

 tion. A significant number of stranded right 

 whales (20%) show major injuries from 

 large-vessel collisions. Young right whales 

 seem particularly vulnerable. A loss of just 

 2-3 calves per year, for example, would 



equal about 10% or more of their annual 

 production. Data needed for a com- 

 prehensive recovery and conservation 

 plan include population trends, life history, 

 and habitat requirements. Far too little data 

 for the blue whale and other species exist 

 to judge whether they are recovering or 

 what other management actions are war- 

 ranted. 



Strandings 



Many bottlenose dolphins died along the 

 U.S. southeast coast in 1987-88, raising 

 questions about coastal pollution and 



whether other species— including hu- 

 mans—could be at risk. However, about 

 half of the Mid-Atlantic nearshore 



