Science Advisory Report 2018/002

Stock assessment for Pacific Herring (Clupea pallasii) in British Columbia in 2017 and forecast for 2018.

Summary

• Commercial fishing for British Columbia (BC) Pacific Herring is managed in five major stock management areas: Haida Gwaii (HG), Prince Rupert District (PRD), Central Coast (CC), Strait of Georgia (SOG), and West Coast of Vancouver Island (WCVI), as well as two minor stock areas: Haida Gwaii Area 2W, and WCVI Area 27.
• For each of the five major areas, spawning biomass in 2017 (SB2017) and pre-fishery forecast spawning biomass for 2018 (SB2018) were assessed. Two base cases were implemented: AM1 and AM2, differing in the treatment of spawn survey scaling coefficients (q1, q2).
• Advice for each Pacific Herring stock in each of the five major areas is presented in decision tables showing predicted status in 2018 given a range of constant catches relative to the limit reference point (LRP) of 0.3SB0, the commercial fishery cut-offs (AM2 only), and target harvest rates of 10% and 20%.
• Sensitivity analyses were conducted to investigate uncertainty in the assumptions that were used to estimate the following parameters: natural mortality, observation and process errors, survey catchability (q1, q2), and maturity at age.
• Resolution between the performance of the AM2 and AM1 model parameterizations of q2 will require a simulation-evaluation analysis. Further details on the analytical concerns with both AM2 and AM1 parameterizations of q1 and q2 can be found in Table A.1 of the 2016 Science Response (DFO 2016).
• The 2017 assessment includes estimation of stock productivity, and current stock status, relative to the limit reference point (LRP) of 0.3SB0 (DFO 2017).
• All five major stocks show declines in weight-at-age from the mid-1980s to 2010, with a levelling off and/or increase in the last five years.
• Potential impacts from the spawn on kelp fishery (SOK) (e.g., mortality, removed spawn) have not yet been formally accounted for in annual stock assessments.
• Other sources of uncertainty include structural assumptions about natural mortality, and uncertainty about the effects of fish movement and stock structure. For two stock areas (HG, WCVI), small sample sizes of age-composition samples in recent years are also a concern.

This Science Advisory Report is from the October 17 & 18, 2017 ‘Stock assessment and management advice for BC Pacific Herring: 2017 status and 2018 forecast’. 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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