Science Advisory Report 2017/043

Pacific Ocean Perch (Sebastes alutus) stock assessments for Queen Charlotte Sound, British Columbia in 2017

Summary

• Pacific Ocean Perch (POP) 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 1977. The stock in Queen Charlotte Sound (5ABC) is the largest of the three POP stocks assessed on the British Columbia coast.
• The stock in area 5ABC was assessed using a single fishery, annual two-sex catch-at-age model, implemented in a Bayesian framework to quantify uncertainty of estimated quantities.
• An update to the 2010 assessment approach was followed, which included the removal of the Queen Charlotte Sound (QCS) shrimp survey series. The QCS shrimp survey series may be evaluated for applicability in future groundfish assessments as well.
• The median (and 5 and 95 percentiles of the Bayesian results) spawning biomass (mature females only) at the beginning of 2017 (B2017) is estimated to be 0.27 (0.18-0.42) of unfished spawning biomass (B0). Also, B2017 is estimated to be 1.03 (0.54-1.96) of the equilibrium spawning biomass at maximum sustainable yield, B_MSY.
• Advice to management is presented in the form of decision tables 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. The decision tables provide five-year projections across a range of constant catches.
• At current catch levels, there is an estimated 0.99 probability that B2017 > 0.4B_MSY, and a 0.74 probability that B2017 > 0.8B_MSY, (i.e. of being in the healthy zone). The probability that the exploitation rate in 2016 was below that associated with MSY is 0.75. Constant catches at levels slightly above the mean of recent catches indicate that there will be slight declines in the probabilities of the spawning biomass being above the reference points at the end of five years.
• A suite of climatic and environmental indicators were investigated to identify potential ecosystem influences on recruitment. The methods used to develop and evaluate the indicators are suitable for identifying ecosystem influences on recruitment, and could be explored with other species.  At present, no link between the indicators and Pacific Ocean Perch recruitment could be detected, consequently ecosystem influences were not incorporated into the model or advice to management.
• It is recommended that the next assessment occur in 2022, with three new indices available from the QCS synoptic trawl survey and five years of ageing and catch data. No appropriate indicators for this stock could be recommended that would trigger an assessment earlier than scheduled. Advice for the interim years is explicitly included in the decision tables.
• Recommended future work includes the investigation of alternative reference points due to the sensitivity of B_MSY based reference points, and the development of informative priors on survey catchability (q).

This Science Advisory Report is from the Regional Peer Review meeting on Stock Assessment for Pacific Ocean Perch (Sebastes alutus) in Queen Charlotte Sound, British Columbia in 2017, held on June 1-2, 2017. Additional publications from this process (Proceedings and Research Document) will be posted the on Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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