Research Document 2018/028

Status of B.C. Pacific Herring (Clupea pallasii) in 2017 and forecasts for 2018

By Cleary, J.S., Hawkshaw, S., Grinnell, M.H., and Grandin, C

Abstract

This document presents a stock assessment for Pacific Herring (Clupea pallasii) in British Columbia using data current to 2017. Results of the work are intended to serve as advice over the short term to fishery managers and stakeholders on current stock status and likely impacts of different harvest options. An updated platform of the integrated combined-sex statistical catch-at-age model (ISCAM) was applied independently to each of the 5 major stock areas and tuned to fishery-independent spawn index data, annual estimates of commercial catch since 1951, and age composition data from the commercial fishery and from the test fishery charter program. Comprehensive stock assessments were done for five major stock areas: Haida Gwaii (HG), Prince Rupert District (PRD), Central Coast (CC), Strait of Georgia (SoG), and West Coast of Vancouver Island (WCVI). Results are summarized as stock reconstructions, status of spawning stock in 2017, and projected spawning biomass in 2018. We also present data for two minor stocks (Area 27; Area 2 West) in Appendix C.

The model estimated stock-recruitment parameters, time-varying natural mortality, catchability coefficients for the survey time series, and selectivity parameters for the commercial fishery and those survey series for which age data are available. Median posterior estimates and 90% credible intervals of spawning biomass, recruitment, time-varying natural mortality, and unfished equilibrium spawning biomass are presented for AM2 and AM1 model parameterizations.

Unfished equilibrium spawning biomass (SB₀) is the main biological reference point used for Pacific Herring and it is estimated from a Beverton-Holt stock-recruitment relationship (parameterized within the assessment model) fitted to longterm average trends in weight-at-age and natural mortality. One-year projections of spawning biomass 2018 were performed for each major stock area over a range of constant catches to estimate probabilities that spawning biomass and harvest rate metrics are below and above control points historically used in the management of Pacific Herring, as specified in the herring harvest control rule. This assessment also includes presentation of current stock status and projected stock status in 2018 relative to a Limit Reference Point (LRP) of 0.3·SB0.

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