Research Document 2024/017
Application of the Management Procedure Framework for Inside Quillback Rockfish (Sebastes maliger) in British Columbia in 2021
By Huynh, Q.C., Siegle, M.R., and Haggarty, D.R.
Abstract
The purpose of this project is to provide scientific advice to support management of Inside Quillback Rockfish (Sebastes maliger). The stock is expected to be prescribed as a major fish stock, at which time its sustainable management will be legislated under the Fish Stocks Provisions of the Fisheries Act. This analysis applied the Management Procedure (MP) Framework, recently developed for British Columbia (BC) groundfishes, to evaluate the performance of index-based and constant catch MPs, with respect to meeting policy and fishery objectives.
To account for uncertainty in underlying population dynamics and data sources, we developed five alternative operating model (OM) scenarios, which differed with respect to specific model and data assumptions. Operating models were conditioned on historical catches, indices of abundance, and age composition. Three reference OMs varied on the assumption of the natural mortality value for Inside Quillback Rockfish. Two additional robustness OMs were developed, with one developed by excluding a historical jig survey in Area 12, and another that modeled lower than average recruitment in the projection. The reference OMs indicated the stock was above the LRP (0.4 BMSY) with at least 50% probability in 2021. The index from the jig survey is impactful on the historical stock trajectory, but is indicative of the declining stock trend that led to the rockfish conservation strategy in the early 2000s.
Two fixed catch MPs of 33 tonnes (the average catch during 2012–2019) and 41 tonnes (125% of the 2012–2019 mean) and eight index-based MPs (Iratio, GB_slope, and IDX with various tuning parameters) that adjust the catch based on the recent trend in the index of abundance from the inside hard-bottom longline (HBLL) survey were tested in the closed-loop simulations. In the reference set, all MPs passed the proposed satisficing criterion with the stock exceeding the LRP with at least 75% probability after one generation (24 years). The satisficing criterion was also met in both robustness operating models.
Visualizations present trade-offs in tabular and graphical formats to support the process of selecting the final MP. There is a trade-off between biomass and fishery catches after one generation with higher catches with Iratio management procedures compared to the others. Tradeoffs in short-term and long-term catch were evident in the short-term (7 years) and after one generation. The tradeoff was less evident over longer time scales (after one vs. three generations or after 24 vs. 72 years). MPs that advise high catches after one generation continue to do so after three generations.
We propose operating models to be identified in the reference set when used to identify stock status. We also provide future research recommendations regarding commercial fishery biological sampling and Food, Social, and Ceremonial (FSC) catch. We make recommendations to use the HBLL index of abundance and HBLL mean weight to identify triggers for future re-assessment.
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