Marine Science Faculty Publications

A Population Assessment of Butterfish, Peprilus triacanthus, in the Northwestern Atlantic Ocean

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Reported landings of butterfish, Peprilus triacanthus (Peck), in the Northwest Atlantic Ocean increased from 3,209 t in 1964 to a peak of 19,454 t in 1973. Most of the catch during the period was taken by vessels from Japan, the United States, Russia, and Poland. Unreported butterfish by-catches in the long-finned squid, Loligo pealei, fisheries of several nations, particularly Spain and Italy, were probably significant additional sources of butterfish mortality. Available scientific evidence indicates that during 1968–1976, fishing mortality rates increased, while the mean weight of individuals in the exploitable population and average age at capture generally declined. Exploitation rate (E) during 1968–1975 averaged 0.31. Yield-per-recruit studies conducted under an assumed instantaneous rate of natural mortality (M) of 0.8 suggest Emax (exploitation rate resulting in maximum yield per recruit) and E0.1 (exploitation rate generating a marginal increase in yield per recruit of 0.1 of that from a lightly exploited fishery) are, respectively, 0.37 and 0.27 for a 30-mm mesh net, and 0.55 and 0.36 for a 60-mm one. Mean weights of fish in the catch, for fishing at E0.1, would be 57% greater for the larger net (66 g) than for the smaller mesh (42 g). Equilibrium yields resulting from an average annual recruitment of 1,138.5 × 106 fish (1968–1975) are about 14,500 t (30-mm mesh) and 19,000 (60-mm mesh), if E0.1 is assumed. The maximum long-term yield from the stock given fluctuations of annual recruitment about the 1968–1975 mean, is approximately 21,500 t, if E0.1 is the maximum exploitation rate that will not adversely affect recruitment.

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Transactions of the American Fisheries Society, v. 108, issue 5, p. 427-439