MARINE MAMMAL COMMISSION — Annual Report for 1991 



The 1991 Tuna Fishing Season 



In 1980, the National Marine Fisheries Service 

 promulgated final regulations establishing annual 

 quotas for individual porpoise stocks and a total 

 annual allowable take for U.S. fishermen of 20,500 

 porpoises for the years 1981-1985. A general permit 

 to take porpoises in compliance with those regulations 

 was also issued in 1980 to the American Tunaboat 

 Association. In 1984, the Marine Mammal Protection 

 Act was amended to extend the annual quotas, the 

 regulations, and the general permit indefinitely and to 

 add quotas for eastern spinner and coastal spotted 

 dolphins. The U.S. fleet continues to operate under 

 the 1980 general permit. 



Estimates of the annual incidental kill of porpoises 

 by the U.S. and foreign tuna purse seine fleets since 

 passage of the Marine Mammal Protection Act are 

 listed in Table 9. Although these are the best avail- 

 able mortality estimates, it should be noted that many 

 of the estimates may not be accurate. Substantial 

 observer coverage of the U.S fleet did not begin until 

 1976 and coverage remained below 50 percent until 

 1987. Observer data for estimating porpoise mortality 

 in the non-U. S. fleet is very sparse for all years prior 

 to 1986. The foreign observer program did not begin 

 in earnest until 1986, when observer coverage was 

 approximately 25 percent. 



More detailed data for the last four fishing seasons 

 are provided in Table 10. In addition to annual 

 dolphin mortality data, information on mortality rates, 

 fishing effort, and observer coverage are presented. 

 The 1991 dataset for non-U. S. vessels is not yet 

 complete, but estimates based on partial-year data are 

 provided. Also, data for revised year 1991 are given 

 for the U.S. fleet. (As discussed below, on 8 October 

 1991, the National Marine Fisheries Service changed 

 the period it would use to make foreign comparability 

 findings from the calendar year to the period from 1 

 October to 30 September. Revised year 1991 covers 

 the period 1 October 1990 to 30 September 1991.) 



Dolphin mortality resulting from U.S. tuna fishing 

 operations in the eastern tropical Pacific during 1991 

 was the lowest since the purse seine fishery began. 

 The single most important factor contributing to the 

 reduced mortality was the 12 April 1990 announce- 

 ment by major U.S. tuna canners that they would no 



longer trade in tuna caught by setting on dolphin and 

 the resulting decrease in sets on dolphins by U.S. 

 vessels. As shown in Table 10, there has been a 

 steady decline In the number of marine mammal sets 

 made by U.S. tuna fishermen over the past four years, 

 with more than a 90 percent decline occurring in the 

 past two years. The low mortality figure for 1991 

 was not solely attributable to abandonment of the 

 practice of setting on porpoises, however. The 

 average dolphin kill for liie U.S. fleet was about 2.5 

 dolphins per set, its lowest mortality rate on record. 



Table 9. Estimated Incidental Kill of Porpois- 

 es in the Tuna Purse Seine Fishery in 

 the Eastern Tropical Pacific Ocean, 

 1972 - 1991' 



Estimates, based on kill per set and fishing effort data 

 provided by the National Marine Fisheries Service and 

 the Inter- American Tropical Tuna Commission, do not 

 include deaths of seriously injured animals released 

 alive. 



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