Research Document - 2000/166

Stock assessment of rock sole and English sole in Hecate Strait for 2000/2001

By J. Fargo, A.R. Kronlund, J.T. Schnute, and R. Haigh

Abstract

The authors summarize biological information and analyse catch-age data for stocks of rock sole and English sole in Hecate Strait. Their analysis uses a state space catch-age model to reconstruct stock histories. Results indicate that recruitment and biomass of both species have declined over the last four years. In particular, recruitments in 1998 and 1999 reached a historic lows for both species. The authors compare biomass estimates from the catch-age analysis with those obtained using swept-area expansions of commercial and research survey catch rates. All analyses show similar stock trends, although estimates have high variability. They use equilibrium calculations to determine various fishing mortality reference points. These suggest lower, more conservative, fishing mortality levels than those found in previous analyses. The authors estimate yield by applying a target fishing mortality to the 1999 estimates of biomass from the catch-age analysis. Current yield recommendations are reduced significantly from previous years. The yield range for rock sole is 600-700 t, while the yield range for English sole is 300-400 t. The authors synthesize this information to provide advice to managers on harvest levels for the 2001/2002 fishing year. 

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