Science Advisory Report  2015/014

Stock assessment for Lingcod (Ophiodon elongatus) for the Strait of Georgia, British Columbia in 2014

Summary

• Lingcod (Ophiodon elongatus) are an important component of both the commercial and recreational groundfish fisheries off British Columbia, Canada.  This stock assessment updates stock status for the inside stock in the Strait of Georgia, British Columbia.
• Large estimated declines in Strait of Georgia Lingcod abundance between 1927 and the late 1980s led to the closure of Lingcod retention by commercial fisheries in this area starting in 1990, and subsequently by the recreational fishery in 2002. Since 2006, a limited recreational fishery has been permitted in some areas of the Strait of Georgia.
• This assessment updates the 2005 assessment framework developed for Strait of Georgia Lingcod with new data, and characterizes how stock status has changed since the current management regime was introduced in 2006.  In addition, spawning biomass levels in 2014 are compared to biomass-based reference points.
• A two-sex statistical catch-at-age model in a Bayesian estimation framework was used. The model was fit to catch data and two indices of abundance, based on fishery catch-per-unit effort.  Age composition data was insufficient for model fitting.
• Nine stock assessment scenarios were used to characterize a range of stock status estimates in 2014. The scenarios differed in: (i) their treatment of historic catch, (ii) assumptions about density-dependent mortality and density-dependent catchability relationships, and (iii) the natural mortality rate M.
• For each scenario, two sets of reference points were used to characterize stock status:  the reference points developed by the 2005 Lingcod Management Framework Committee, which are relative to unfished spawning biomass, B₀, and provisional reference points identified by the more recent DFO Decision-making Framework Incorporating the Precautionary Approach (DFO PA Framework), which are relative to the level of spawning biomass associated with maximum sustainable yield, B_MSY.
• In all scenarios, spawning biomass in 2014 was predicted with 100% certainty to be greater than spawning biomass at the start of the current management regime in 2006.  However, current stock status relative to reference points was dependent on both the treatment of historical catch from the Dominion Bureau of Statistics’ District 1 (1927-1946) and the assumption made about density-dependent catchability.
• When the 2005 Lingcod Management Framework reference points were used to classify stock status, two of nine scenarios estimated that B₂₀₁₄ was most likely above the short-term recovery target of 0.25B₀ but below the long-term recovery target of 0.40B₀, while the remaining seven scenarios estimated that B₂₀₁₄ was most likely above the limit reference point of 0.10B₀, but below 0.25B₀.  A model-averaging approach to status estimation, in which the Bayesian posterior distributions from all nine scenarios were combined with equal weights, estimated that B₂₀₁₄ had a 71% probability of being between the limit reference point (0.10B₀) and the short-term recovery target (0.25B₀).
• When the DFO PA Framework reference points were used to classify stock status, six of nine scenarios estimated that B₂₀₁₄ was most likely in the cautious zone (between 0.4B_MSY and 0.8B_MSY, while the remaining three scenarios estimated that B₂₀₁₄ was most likely in the critical zone (below 0.4B_MSY).  The model-averaging approach estimated that B₂₀₁₄ had a 58% probability of being in the cautious zone, a 37% probability of being in the critical zone, and a 5% probability of being in the healthy zone (above 0.8B_MSY).
• No harvest advice was requested.

This Science Advisory Report is from the December 10-11, 2014 Lingcod Assessment (Ophiodon elongatus) for the Strait of Georgia (Area 4B), British Columbia in 2014. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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