Application of the management procedure framework for inside quillback rockfish (Sebastes maliger) in British Columbia in 2021

Abstract

The inside stock of Quillback Rockfish (Sebastes maliger, Inside Quillback Rockfish) occurs in Groundfish Management Area 4B (Queen Charlotte Strait, Strait of Georgia, and Strait of Juan de Fuca) in British Columbia (BC). This analysis provides scientific advice for the sustainable management of Inside Quillback Rockfish consistent with the Precautionary Approach (PA) Policy through application of the Management Procedure (MP) Framework developed for BC groundfishes (Anderson et al. 2021). The MP Framework evaluates the performance of MPs across alternative plausible states of nature explored in different operating models (OMs). Current stock status partly determines management actions related to policy requirements. The stock status was evaluated with regard to a Limit Reference Point (LRP) and Upper Stock Reference (USR) of 0.4 BMSY and 0.8 BMSY, respectively. The 2021 spawning biomass was estimated to be 88% of BMSY (with an interquartile range of 46-147% credible interval (CI)), above the LRP with a 79% probability, and above the USR with a 52% probability, averaged across three OMs. Since the current stock biomass is estimated to be above the LRP, the conservation objective is to maintain the stock above the LRP after one generation (24 years) with a minimum probability of 75%. Other objectives include maintaining the stock above the USR, and maintaining fishery access and catch. These objectives follow strategic objectives identified in workshops held in 2021 (see Haggarty et al. 2022). The generation time was estimated to be 24 years, based on the natural mortality value of 0.067 and 50% maturity at 8.7 years. Natural mortality is based on the maximum observed age of 80 years. Since the previous assessment, the relationship between natural mortality and maximum observed age has been updated based on meta-analyses in the scientific literature. Five total OMs were explored. Three reference OMs differ in values of mean natural mortality (M = 0.067, 0.055, 0.088). Two robustness OMs include an OM that excludes Area 12 jig survey data, and an OM that assumes low future recruitment. Environmental conditions affecting stock dynamics were considered with the alternative values of natural mortality and low recruitment OMs. Our understanding of the environment and stock productivity, however, is not sufficient to model these relationships mechanistically. The Management Procedures (MPs) evaluated included two constant catch MPs, eight MPs based on an index of survey abundance, and a “no fishing” and “fishing at FMSY” reference MP. All MPs met the conservation objective of being above the LRP after one generation with 75% probability under the OM reference set scenarios. A trade-off between maintaining the stock above the LRP after one generation, and maximizing catch over one generation was identified across the candidate MPs. Minimal trade-off between catch after one generation and catch after three generations was observed. MPs that advise high catches after one generation continue to do so after three generations. Since index-based management procedures were implemented biennially in the projections, we recommend updating the catch advice from the selected MP (if index-based) every two years. Exceptional circumstances that would trigger a re-evaluation of the OMs should be reviewed on a regular basis.