MARINE MAMMAL COMMISSION - Annual Report for 1995 



merit period. Preparation of draft stock assessments 

 and the Commission's comments on them are dis- 

 cussed in the previous annual report. 



Within 90 days of the close of the public comment 

 period on the draft stock assessments, the Secretary 

 was to issue final stock assessments. Each assessment 

 was to (1) describe the geographic range of the stock, 

 (2) provide a minimum population estimate, the 

 stock's current and maximum net productivity rates, 

 and current population trend, including the basis for 

 those findings, (3) estimate the annual human-caused 

 mortality and serious injury, by source, and, for 

 stocks determined to be strategic stocks, describe 

 other factors that may be causing a decline or imped- 

 ing recovery, (4) describe the commercial fisheries 

 that interact with the stock, including estimates of 

 fishery-specific mortality and serious injury levels and 

 rates, a description of seasonal or area differences in 

 incidental take, and an analysis of whether incidental- 

 take levels are approaching a zero mortality and 

 serious injury rate, (5) assess whether the level of 

 human-caused mortality and serious injury would 

 cause the stock to be reduced below its optimum 

 sustainable population or, alternatively, whether the 

 stock should be categorized as a strategic stock, and 

 (6) estimate the potential biological removal level for 

 the stock. 



As defined in the Act, a stock's potential biological 

 removal level is the maximum number of animals, not 

 including natural mortality, that can be removed from 

 the stock while allowing the stock to reach or remain 

 at its optimum sustainable population level. The 

 potential biological removal level is calculated by 

 multiplying three variables — the minimum population 

 estimate for the stock, one-half of the theoretical or 

 estimated maximum net productivity rate of the stock 

 at a small population size, and a recovery factor of 

 between 0.1 and 1.0. Strategic stocks are those that 

 (a) have a level of direct human-caused mortality 

 exceeding the calculated potential biological removal 

 level, (b) are designated as depleted under the Marine 

 Mammal Protection Act, (c) are listed as endangered 

 or threatened under the Endangered Species Act, or 

 (d) are likely to be listed as endangered or threatened 

 in the foreseeable future. 



On 25 August 1995 the National Marine Fisheries 

 Service published a notice in the Federal Register 

 announcing the availability of the final stock assess- 

 ments for species under its jurisdiction. The stock 

 assessments were released as three National Oceanic 

 and Atmospheric Administration technical memoranda 

 covering, respectively, stocks occurring in Alaska, the 

 Pacific, and the Atlantic and Gulf of Mexico. The 

 Service also published a separate report describing the 

 guidelines used in preparing the stock assessments and 

 summarizing the information in the assessments. 



Assessments were prepared for 34 stocks of 

 cetaceans and pinnipeds along the U.S. Atlantic coast. 

 Sixteen of those were determined to be strategic 

 because the estimated annual mortality incidental to 

 commercial fisheries exceeds the stock's potential 

 biological removal level. As discussed in Chapter HI, 

 the Gulf of Maine stock of harbor porpoise is being 

 hit particularly hard by fisheries-related mortality, 

 with incidental mortality in the sink gillnet fishery 

 exceeding the potential biological removal level by 

 more than a factor of four. The Service found the 

 Atlantic drift gillnet fishery for swordfish, shark, and 

 tuna to be primarily responsible for 13 of the stocks 

 being classified as strategic but noted that frequent 

 mortality also occurs in the pair-trawl fishery for 

 swordfish, shark, and tuna, the longline fishery for 

 swordfish, tuna, and billfish, the New England 

 groundfish trawl fishery, and perhaps the mid-water 

 trawl fisheries for mackerel and squid. The Service 

 cautioned, however, that some of the stocks may have 

 been determined to be strategic because of difficulty 

 in differentiating certain species, such as beaked 

 whales and pilot whales. None of the 26 cetacean 

 stocks occurring in the Gulf of Mexico was deter- 

 mined to be a strategic stock due to fisheries-related 

 mortality. 



The National Marine Fisheries Service also pre- 

 pared assessments for 34 cetacean and pinniped stocks 

 off California, Oregon, and Washington. For seven 

 of those stocks, estimated mortality incidental to com- 

 mercial fisheries exceeds the potential biological 

 removal level. Incidental mortality involving these 

 stocks results almost exclusively from the drift gillnet 

 fishery for swordfish and shark. Of the 20 stocks of 

 marine mammals that occur in Hawaiian waters and 

 the 31 marine mammal stocks under National Marine 



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