An evidence-based approach for selecting a limit reference point for Pacific herring (Clupea pallasii) stocks in British Columbia, Canada

Abstract

A limit reference point (LRP) is defined as a level of biomass to be avoided with high probability, which should be selected to protect fish stocks from “serious harm”. We present an evidence-based approach for diagnosing serious harm and apply it to the selection of LRPs for five Pacific herring ( Clupea pallasii) stocks in British Columbia (BC). Natural mortality ( M) is estimated to be time varying and has increased more than it declined over the past three decades, which presents a challenge for estimation of equilibrium reference points based on maximum sustainable yield. We present a semi-empirical approach for developing LRPs, which examines surplus production in relation to spawning biomass to determine whether there is evidence for low productivity, low biomass (LP-LB) states consistent with serious harm. Three stocks showed evidence of persistent LP-LB states that resulted in periods of fishery closures. Based on these results, an LRP of 30% of unfished spawning biomass (0.3 B0) was recommended and adopted for management of all five major stocks of BC Pacific herring.