Science Advisory Report  2013/038

Pacific Ocean Perch (Sebastes alutus) stock assessments for the west coast of Vancouver Island and the north and west coasts of Haida Gwaii, British Columbia

Summary

• Pacific Ocean Perch is a commercially important species of rockfish that has supported a domestic trawl fishery for decades, and was heavily fished by foreign fleets from the mid-1960s to the mid-1970s.
• The stocks in areas 3CD and 5DE are assessed as two independent stocks using an annual two-sex catch-at-age model, implemented in a Bayesian framework to quantify uncertainty of estimated quantities.
• This is the first time that a population dynamics model has been used to assess either stock.
• For area 3CD, the spawning biomass (mature females only) at the beginning of 2013 (B2013) is estimated to be 0.41 (0.19-0.68) of unfished spawning biomass (B0); numbers denote median (and 5-95 percentiles) of the Bayesian results. Also, B2013 is estimated to be 1.53 (0.55-3.32) of the equilibrium biomass at maximum sustainable yield, B_MSY.
• For area 5DE, B2013 is estimated to be 0.37 (0.16-0.67) of B0, and 1.61 (0.57-3.57) of B_MSY.
• An exceptionally strong recruitment of age-1 fish in 1977 was estimated for the stock in area 5DE, though not for area 3CD.
• Decision tables are presented using the provisional reference points from the Fisheries and Oceans Canada Sustainable Fisheries Framework Precautionary Approach, namely a limit reference point of 0.4B_MSY and upper reference point of 0.8B_MSY. For area 3CD, B2013 is estimated to have a 0.99 probability of being >0.4B_MSY, and a 0.87 probability of being >0.8B_MSY (i.e. of being in the healthy zone). The probability that the exploitation rate in 2012 was below that associated with _MSY is 0.89.
• For area 5DE, B2013 is estimated to have a 0.98 probability of being >0.4B_MSY, and a 0.88 probability of being >0.8B_MSY. The probability that the exploitation rate in 2012 was below that associated with _MSY is 0.84.
• Advice to management is presented in the form of decision tables using ten-year projections for a range of constant catches. For both stocks, catches at levels slightly above recent mean catches indicate essentially no change in the aforementioned probabilities of the spawning biomass being above the reference points.

This Science Advisory Report is from the Regional Peer Review meeting on ‘Stock Assessments for Pacific Ocean Perch in Areas 3CD and 5DE (British Columbia)’, held on November 6-7, 2012. Additional publications from this process (Proceedings and two Research Documents) will be posted the on Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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