Science Advisory Report  2011/051

Lingcod (Ophiodon Elongatus) Stock Assessment and Yield Advice for Outside Stocks in British Columbia

Summary

• Lingcod (Ophiodon elongatus) are an important component of both the commercial and recreational groundfish fisheries off British Columbia, Canada.  They are exploited primarily by trawl, but also by hook and line, including handline, longline and troll. They have a long history of exploitation as food fish, starting with First Nations as early as 5,000 years ago, and it known that they were fished by early settlers in the inshore waters around Victoria by the mid-1800s. Catch data are available from 1927.
• Outside lingcod populations in British Columbia are assessed and managed as four separate units based on DFO Statistical Areas: southwest Vancouver Island (Area 3C), northwest Vancouver Island (Area 3D), Queen Charlotte Sound (Areas 5A and 5B), and Hecate Strait and the west coast of Haida Gwaii (Areas 5C, 5D, and 5E).
• A Bayesian surplus production model was used to assess lingcod stock status within each of the four assessment areas.  Data inputs included at least three relative abundance (trawl survey or CPUE) indices (with CV’s), and prior probability distributions for estimated parameters.Area-specific parameter estimates for intrinsic rate of increase (r) and carrying capacity (K) were used to calculate management parameters such as maximum sustainable yield (MSY), the optimum fishing mortality rate at MSY (F_MSY), and the optimal stock size at MSY (B_MSY). The assessment model was projected 5 years into the future under a range of alternative constant harvest policies (e.g., total allowable catch levels), to produce decision tables for each assessment area.  Sensitivity analyses were used to evaluate the effect of stock assessment assumptions on the results.
• For Area 3C, the median of the estimated posterior distribution for B₂₀₁₀ is 111% of B_MSY, indicating that this stock is most likely in the Healthy Zone.  Greater uncertainty exists in stock status estimates for Area 3C than other Areas because the probability that B₂₀₁₀ is in the Healthy Zone is only 67% and the probability that B₂₀₁₀ is in the Critical Zone is 10%.
• For Area 3D, the median of the estimated posterior distribution for B₂₀₁₀ is 156% of B_MSY, indicating that this stock is most likely in the Healthy Zone.  There is high confidence in classifying the Area 3D stock as “Healthy” because the probability that B₂₀₁₀ is in the Healthy Zone is 95% and the probability that B₂₀₁₀ is in the Critical Zone is < 1%.
• For Area 5AB, the median of the estimated posterior distribution for B₂₀₁₀ is 113% of B_MSY, indicating that this stock is most likely in the Healthy Zone. There is greater uncertainty in stock status estimates for Area 5AB than in Area 3D and 5CDE because the probability that B₂₀₁₀ is in the Healthy Zone is only 67%, and the probability that B₂₀₁₀ is in the Critical Zone is 5%.
• For Area 5CDE, the median of the estimated posterior distribution for B₂₀₁₀ is 146% of B_MSY, indicating that this stock is most likely in the Healthy Zone.  There is high confidence in classifying the Area 5CDE stock as “Healthy” because the probability that B₂₀₁₀ is in the Healthy Zone is 88% and the probability that B₂₀₁₀ is in the Critical Zone is < 1%.

This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, Regional Advisory Meeting of April 7-8, 2011 on Reviews of stock assessments for outside stocks of lingcod and inside stocks of yelloweye rockfish in British Columbia.  Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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