Science Advisory Report 2020/056

Evaluation of Management Procedures for the Inside Population of Yelloweye Rockfish Rebuilding Plan

Summary

• The inside stock of Yelloweye Rockfish (Sebastes ruberrimus, Inside Yelloweye Rockfish) is a data-limited stock, occurring in Groundfish Management Area 4B (Queen Charlotte Strait, Strait of Georgia, and Strait of Juan de Fuca) in British Columbia (BC).
• The stock was assessed as being below the Limit Reference Point (LRP) in 2010, resulting in a published rebuilding plan.
• This assessment provides scientific advice through application of a new management strategy evaluation framework recently developed for BC groundfishes (the Management Procedure [MP] Framework) (Anderson et al. 2021). The MP Framework evaluates the performance of alternative data-limited MPs to support re-evaluation of the current rebuilding plan for Inside Yelloweye Rockfish.
• The MP Framework was used to evaluate the ability of 34 data-limited MPs to meet the proposed principal objective of rebuilding the stock above the LRP (0.4 BMSY) over 1.5 generations (56 yrs) with at least a 95% (19 times out of 20) probability of success.
• Performance of MPs was also evaluated for two additional conservation metrics based on LRP=0.4BMSY and Upper Stock Reference (USR)=0.8BMSY, three average-catch objectives, and one catch-variability objective.
• Natural mortality, selectivity, and historical catch were identified as major sources of uncertainty. Uncertainty in these parameters was accounted for by evaluating performance of the MPs across six alternative Operating Models (OM) scenarios based on different model and data assumptions. Four OMs, representing the most important and plausible uncertainties, were allocated to a “reference set”; two OMs, representing a broader range of uncertainties, were allocated to a “robustness set”. 
• None of the reference set OMs estimated the median stock biomass to be below the LRP in 2019.  Differences in estimates of Inside Yelloweye Rockfish stock status between the current OMs and previous assessment were attributable to model structure choices.
• Closed-loop simulation screened out MPs that did not meet basic performance criteria, resulting in five remaining candidate MPs: two annual constant-catch MPs (10 and 15 tonnes), and three MPs that adjust the total allowable catch (TAC) based on a survey index of abundance. All five final MPs met the principle performance metric with greater than 0.98 probability (49 times out of 50), across all four OM reference set scenarios.
• The constant catch policy MPs resulted in a greater short-term fishery yield and higher catch stability than the index-based MPs. Index-based MPs resulted in greater long-term yield.
• MP performance was most challenged under the lower productivity robustness scenario (Low M), where none of the five MPs were able to achieve the principle performance metric. The highest-ranking MP for this scenario (a constant catch of 10 tonnes) resulted in a 90% probability of rebuilding the stock to above the LRP over 1.5 generations.
• Based on performance relative to the objectives, the rank order of the five candidate MPs was consistent among reference set scenarios with the highest ranking MP consistently being the constant annual catch  of 10 t. This was also the highest ranking MP for both robustness set scenarios.
• Major uncertainties associated with assessing stock status for Inside Yelloweye Rockfish highlight the importance of using an MP framework for decision-making.
• For the five final candidate MPs, the catch advice from the index-based MPs should be updated annually. Prospective performance of all MPs should be re-evaluated at least every three years.
• Establishing formal “exceptional circumstance” detection protocols to trigger earlier reevaluation of performance of the chosen MP is recommended.
• The flexibility of the MP Framework to inform different information needs was demonstrated using results structured to allow evaluation of two additional assessment criteria for the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).
• This was the first implementation of the MP Framework for decision making. Future collaborative work is recommended to identify further management objectives for Inside Yelloweye Rockfish.

This Science Advisory Report is from the June 10-11, 2020 regional peer review on the Evaluation of Management Procedures for the Inside Population of Yelloweye Rockfish Rebuilding Plan. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Scheduleas they become available. Publications from the Canadian Science Advisory Secretariat (CSAS) regional peer review (RPR) held on June 8-9, 2020, titled ‘A Management Procedure Framework for British Columbia Groundfish’, should be viewed as companion documents.

Science Advisory Report 2020/056 (PDF, 2,440 KB)

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