Survey- and fishery-derived estimates of Pacific cod (Gadus macrocephalus) biomass: implications for strategies to reduce interactions between groundfish fisheries and Steller sea lions (Eumetopias jubatus)

• Main Authors: Fritz, Lowell W., Brown, Eric S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2005
• Subjects: Biology; Ecology; Fisheries; Bering Sea; Pacific; Aleutian Islands
• Online Access: http://hdl.handle.net/1834/26213

Survey- and fishery-derived biomass estimates haveindicated that the harvest indices for Pacific cod (Gadus macrocephalus) within a portion of Steller sea lion (Eumetopias jubatus) critical habitat in February and March 2001 were five to 16 times greater than the annual rate for the entire Bering Sea-Aleutian Islands stock. A bottomtrawl survey yielded a cod biomass estimate of 49,032 metric tons (t) for the entire area surveyed, of whichless than half (23,329 t) was located within the area used primarily by the commercial fishery, which caught 11,631 t of Pacific cod. Leslie depletion analyses of fishery data yielded biomass estimates of approximately 14,500 t (95% confidence intervals of approximately 9,000–25,000 t), whichare within the 95% confidence interval on the fished area survey estimate (12,846–33,812 t). These data indicatethat Leslie analyses may be useful in estimating local fish biomass and harvest indices for certain marine fisheries that are well constrained spatially and relatively short in duration (weeks). In addition, fishery effects on prey availability within the time and space scales relevantto foraging sea lions may be much greater than the effects indicated by annual harvest rates estimated from stock assessments averaged across the range of the target spec