Slope rockfish stock assessment for the west coast of Canada in 1996 and recommended yields for 1997 / by L.J. Richards and N. Olsen.: Fs97-6/2134E-PDF

"This document contains a major update of the stock status for slope rockfish that was presented to the Pacific Stock Assessment Review Committee (PSARC) in 1996. For assessment purposes, slope rockfish include Pacific ocean perch, redstripe rockfish, yellowmouth rockfish, rougheye rockfish, shortraker rockfish and shortspine and longspine thornyheads. The best information is for the Goose Island Gully stock of Pacific ocean perch. A catch-age analysis for this stock uses catch-age data available from 1963-95 and a series of trawl surveys, updated with recent surveys in 1994 and 1995. Based on this analysis, the foreign fishery of the late 1960s and early 1970s reduced the stock to about a third of the 1965 exploitable biomass by 1977. Between 1977-84, biomass remained relatively constant. Biomass then increased to over half of the 1965 level by 1995, as a result of above-average recruitment and low fishing morality rates. The stock is now at an average level of abundance. Biomass is predicted to decrease under higher fishing mortality rates unless recruitment is above average. Because of limited data, we are less certain about the status and potential yields of other stocks of Pacific ocean perch. Yields for redstripe rockfish, yellowmouth rockfish and shortspine thornyheads are derived from percentages of the Pacific ocean perch yield. Percentages are expanded from Goose Island Gully bottom trawl survey information, after considering potential midwater abundance and recent ratios in the catch. Yields for rougheye rockfish are based on the species longevity of up to 147 years of age. Yields for shortraker rockfish are determined from the ratio of shortraker to rougheye rockfish in monitored landings. We have no scientific basis for recommending yields for longspine thornyheads"--Abstract, page iii.

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