CHAPTER IV 
INCIDENTAL TAKE OF MARINE MAMMALS IN THE COURSE 
OF COMMERCIAL FISHING OPERATIONS: 
THE TUNA-PORPOISE ISSUE 
The Marine Mammal Protection Act directs the Secretary of 
Commerce, in consultation with the Commission, to develop 
regulations governing the incidental taking of marine mammals 
by persons subject to the jurisdiction of the United States 
and to develop effective international arrangements, through 
the Secretary of State, for the purpose of reducing the 
incidental taking of marine mammals to insignificant levels 
approaching a zero mortality and serious injury rate. 
Although incidental taking of marine mammals occurs in 
the course of several fisheries and involves several different 
species of marine mammals, the "tuna-porpoise" issue involving 
the incidental mortality and serious injury of porpoises 
entrapped in the purse seine nets used by commercial yellowfin 
tuna fishermen has been the subject of the most intense concern, 
attention, and controversy since passage of the Act. 
A detailed discussion of the Commission's activities and 
an historical summary of efforts to resolve the problem are 
presented in the Commission's previous Annual Reports. During 
1980, the Commission continued to devote efforts to this 
aspect of incidental taking of marine mammals, with particular 
attention to regulations governing the 1981-1985 fishing 
seasons, population assessment, and research planning, as 
described below. 
The 1980 Fishing Season 
As discussed in the Commission's previous Annual Reports, 
final regulations governing the 1978-1980 fishing seasons 
were published by the National Marine Fisheries Service in 
the Federal Register on 23 December 1977. These regulations 
established declining incidental take quotas of 51,945 
animals in 1978,.41,610 in 1979, and 37;150 an 1980. Al- 
though analyses have not yet been completed and a final 
figure is not yet available, the data available at the end 
of 1980 indicate that, as in 1978 and 1979, the U.S. fishing 
fleet maintained the total porpoise mortality and serious 
injury level well below the upper limits established by the 
quotas and that the total incidental porpoise mortality and 
serious injury associated with U.S. commercial yellowfin 
tuna fishing in 1980 was between 13,000 and 15,000 animals. 
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