Revised estimates of incidental kill of dolphins (Delphinidae) by the purse-seine tuna fishery in the eastern tropical Pacific, 1959-1972

Wade, P.R.

U S National Marine Fisheries Service Fishery Bulletin 93(2): 345-354

1995


Accession: 009357433

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Abstract
Dolphins (Delphinidae) have been killed incidentally by the purse-seine fishery for yellowfin tuna, Thunnus albacares, in the eastern tropical Pacific since at least 1959. Annual estimates of the number of dolphins killed from each stock are used by the National Marine Fisheries Service in making management decisions about the population status of affected stocks. Mortality estimates from the period with the greatest kill of dolphins, 1959-72, are important for estimates of the level of depletion of these stocks from their unexploited population sizes. A redefinition of the geographical boundaries of offshore stocks of pantropical spotted dolphins, Stenella attenuata, makes it necessary to estimate annual kill for these new defined stocks for 1959-72. I estimated number of dolphins killed annually from 1959 to 1972 for the northeastern and western/southern stocks of spotted dolphins, using the methods of Lo and Smith (1986). I also revised the estimates of annual kill for the eastern and whitebelly stocks of spinner dolphins, S. longirostris, by correcting minor problems in previous data and analyses. Additionally, I estimated a coefficient of variation (CV) for each stock-specific estimate of incidental kill, which had not previously been done. Estimates of total kill were similar to previous estimates: 4.9 million dolphins are estimated to have been killed by the purse-seine fishery over the fourteen year period considered here, an average of 347,082 per year. Nearly all of the fisheries kill of pantropical spotted dolphins was of the northeastern stock, totaling 3.0 million (211,612 per year). Estimates of kill for the eastern stock of spinner dolphins were similar to previous estimates, totaling 1.3 million (91,739 per year). As expected, CVs of the kill for each stock were higher than those previously reported for the total kill.