Science Advisory Report  2011/060

Recovery Potential Assessment for Yellowmouth Rockfish (Sebastes reedi) along the Pacific Coast of Canada

Summary

• The assessment considered Yellowmouth Rockfish along the Pacific coast of Canada as a single stock. Over the last 15 years, the British Columbia trawl fleet has encountered Yellowmouth Rockfish over an estimated 29,500 km².
• A two-sex, age-structured model was used to estimate biomass from 1940 to 2011, and to make projections under a range of constant catch scenarios. Model results are reported for the two accepted model runs (the first estimated natural mortality, M, and the second kept it fixed); values are the medians followed by the 5-95% credible intervals derived from Bayesian output.
• The results imply a slow-growing population that experienced relatively long periods of low recruitment punctuated by occasional episodes of high recruitment, one in the early 1960s and another in the early 1980s.
• Estimates for the ratio of spawning biomass (mature females only) at the beginning of 2011 to the unfished equilibrium spawning biomass are 0.61 (0.43-0.83) and 0.41 (0.29-0.55) for runs ‘Estimate M’ and ‘Fix M’ respectively.
• Exploitation rates for 2010 are estimated to be 0.020 (0.010-0.036) for run ‘Estimate M’ and 0.038 (0.026-0.059) for run ‘Fix M’, compared to respective historic highs of 0.090 (0.059-0.123) and 0.130 (0.110-0.154) estimated for 1966 during intense fishing by foreign fleets.
• Current and projected probabilities of the status of the population are given with respect to (i) the DFO Sustainable Fisheries Framework provisional reference points, (ii) reference points of 0.2B₀ and 0.4B₀ (where B₀ is the equilibrium unfished spawning biomass), and (iii) reference criteria given by COSEWIC assessment indicators A1 and A2.
• Projections are presented for up to three generations (90 years) for both model runs. For each level of constant catch, these give probabilities of future population status with respect to the above reference points and reference criteria, as well as estimates of the time taken to attain them (with different levels of confidence).

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, Regional Advisory Process meeting held on 30th May 2011, reviewing Working Paper 2010/035 Stock assessment and recovery potential assessment for Yellowmouth Rockfish (Sebastes reedi) along the Pacific coast of Canada. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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