Science Advisory Report  2011/017

Stock assessment for Pacific ocean perch (Sebastes alutus) in Queen Charlotte Sound, British Columbia in 2010

Summary

• Pacific ocean perch supports the largest rockfish fishery in British Columbia with an annual coastwide TAC (total allowable catch) of 6,148 t.  The trawl fishery receives 99.98% of the coastwide TAC, with the rest allocated to the hook and line fishery.
• Stock status was assessed using an annual two-sex catch-at-age model tuned to three fishery-independent trawl survey series (Goose Island Gully historic, Queen Charlotte Sound synoptic and Queen Charlotte Sound shrimp), annual estimates of commercial catch since 1940, and age composition data from two of the survey series (8 years) and the commercial fishery (29 years). Results presented herein are reported for the two accepted model runs (the first estimated natural mortality and the second kept it fixed); numeric ranges refer to the 5 to 95% credible intervals derived from Bayesian output.
• Spawning biomass (mature females only) at the beginning of 2011 is estimated to be in the range of 12-43% or 8-24% of the equilibrium unexploited value.
• Annual exploitation rates have increased since the 1980s, and are approaching or have reached the historic high levels associated with the large catches by foreign fleets in the late 1960s. The exploitation rate for 2010 is estimated to be in the range 0.041-0.152 or 0.089-0.224.
• Based on the DFO Sustainable Fisheries Framework, Precautionary Approach compliant limit and upper reference points of 0.4B_MSY and 0.8B_MSY were calculated (where B_MSY is the spawning biomass at the maximum sustainable yield).  The spawning biomass at the start of 2011 has a probability of 0.96 or 0.82 of being above 0.4B_MSY, and of 0.68 or 0.24 of being above 0.8B_MSY.
• Constant catch projections at 3,500 t/year (which is the average catch from 2006 to 2010) over 5 years predict that the spawning biomass at the start of 2016 would have a probability of 0.91 or 0.57 of remaining above 0.4B_MSY, and of 0.63 or 0.15 of remaining above 0.8B_MSY.
• Both model runs estimate that since 1981 there have been no recruitment events as large as those observed in the early 1950s and late 1970s. There is evidence that an above average recruitment event occurred in the early 2000s, although there have been insufficient observations of this year class to be confident of its size.

This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat Pacific Regional Advisory Meeting of November 24, 2010 on Stock Assessment for Pacific Ocean Perch (Sebastes alutus) in Queen Charlotte Sound, British Columbia.  Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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