Application of Management Procedure Framework for Outside Quillback Rockfish

The outside stock of Quillback Rockfish (Sebastes maliger, Outside Quillback Rockfish) occurs in all coastal waters outside of Groundfish Management Area 4B in British Columbia (BC). This analysis provides scientific advice for the sustainable management of Outside 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). The stock status was evaluated with regards 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 189% of BMSY (standard deviation (SD) = 13%), and above both the LRP and USR with a 99% probability, averaged across three reference OMs. Since the current stock biomass is estimated to be above the LRP, the conservation objectives are to maintain the stock: (1) above the LRP during two generations (54 years) with a minimum probability of 75%, (2) above the USR with a minimum probability of 50%; and to (3) maintain fishing mortality below the removal reference, i.e., FMSY, with a minimum probability of 50%. Other objectives include 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 27 years, based on the natural mortality value of 0.056 and 50% female maturity at 9.4 years. Natural mortality is based on the maximum observed age of 95 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) and the assumption that recreational catch is lower than estimates from the Internet Recreational Effort and Catch (iREC) survey. Two robustness OMs include an OM with lower steepness (h), and an OM that assumes lower average future recruitment. Environmental conditions affecting stock dynamics were considered with the alternative values of natural mortality, steepness, and lower recruitment OMs. Our understanding of the environment and stock productivity is not sufficient to model these relationships mechanistically. The Management Procedures (MPs) evaluated included three constant catch MPs, eight MPs based on an index of survey abundance, and a “no fishing” and “fishing at FMSY” reference MP. All MPs (except one of the constant catch MPs, which did not meet the removal reference criterion) met all three conservation objectives under the OM reference set scenarios. Among the set of satisficed MPs, there is a trade-off between long-term biomass levels and long-term catches. While the MPs varied in the levels of long term catch, all maintained a high to very high probability of staying above the LRP and USR during the projections. The index-based management procedures were implemented biennially in the projections because the hard bottom longline (HBLL) survey requires two years to sample the full area. As such, catch advice from the index-based MPs can only be updated every two years. Exceptional circumstances that would trigger a re-evaluation of the OMs will be reviewed using the survey index, age and size-structure, and life history parameters. These data are presented in the Groundfish (GF) Synopsis report (e.g., DFO 2022).

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