Research Document - 1999/195

Sablefish Stock Assessment for 1999 and Recommended Yield Options for 2000 and 2001.

By V. Haist, R. Hilborn, and M. Saunders

Abstract

This document represents a major assessment for B.C. sablefish. The principle data source on trends in abundance is the tagging program, and in particular the percentage of tags returned in the year following tagging. Coastwide, this percentage remained steady at 10-11% from 1991 to 1997, but rose to 14% in 1998.

Analytical stock assessments are conducted using an integrated catch-age mark-recapture model. The stock reconstructions suggest that from 1972 to 1998 the available biomass of sablefish decreased by 50% in northern B.C. and by 48% in southern B.C. The 1998 female spawning stock biomass (SSB) is estimated at 50-67% of the virgin level for the southern B.C. stock, and from 38-48% of the virgin level for the northern B.C. stock. These SSB levels are well above "high risk" levels, hence, there are no short-term conservation concerns for these stocks.

Deterministic stock projections are conducted for the 2000 to 2008 period at three levels of fixed harvest. Stock projections suggest that current removals in the north are not sustainable, and that in the next 8 years considerable reduction in removals from the north may be required if recruitment does not increase. Recent reductions in trawl by-catch and reduced mortality of small sablefish from escape rings may result in increased recruitment.

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