Science Advisory Report 2021/002
A Management Procedure Framework for Groundfish In British Columbia
- For data-limited stocks, data are often insufficient to use traditional stock assessments to determine stock status relative to biological reference points.
- Instead, a management procedure (MP) framework is proposed that emphasizes selecting MPs that have a specified probability of maintaining fish stocks above implicitly known reference points across multiple plausible states of nature.
- A reference point may not be explicitly known and so cannot be expressed as, for example, a spawning biomass of 10,000 t. Instead, the probability that the stock will remain above the reference point under a given MP can be calculated.
- The MP framework evaluates the performance of MPs with respect to attaining pre-defined objectives. Objectives are quantitatively expressed in terms of performance metrics; reference points can be implicit components of metrics.
- Worldwide there has been a movement towards MP (or management strategy evaluation) approaches to providing science advice on fish stocks via closed-loop simulation. Closed-loop simulation differs from conventional stock assessment because it simulates feedback between the implementation of MPs and the system representing the fish stock and its environment, described by one or more operating models (OMs).
- This document presents a methodology for developing appropriate OMs, testing suites of MPs, and identifying MPs that best meet the objectives of fisheries management, stakeholders and First Nations, specifically for British Columbia (BC) groundfish.
- The proposed MP framework is described according to how it aims to accomplish each of six best-practice steps for MP approaches: (1) defining the decision context, (2) setting objectives and performance metrics, (3) specifying OMs, (4) selecting candidate MPs, (5) conducting closed-loop simulations, and (6) presenting results to evaluate trade-offs.
- The framework includes (1) provisional conservation objectives, fishery objectives, and performance metrics based on policies of Fisheries and Oceans Canada’s Sustainable Fisheries Framework, (2) a provisional library of data-limited MPs that are appropriate for BC groundfish stocks, and (3) provisional visualizations to help decision-makers evaluate performance of MPs and trade-offs among MPs.
- Steps 3 to 5 of the framework are the primary responsibility of the DFO Science Branch, though wider engagement at all steps will lead to greater credibility of the process and chances of its successful implementation. Ultimately, it is the role of Fisheries Management, with input from Science, stakeholders, and First Nations, to select the final MP that delivers a total allowable catch with acceptable tradeoffs.
- All code for implementing the MP Framework is publicly available in existing and custom-built R packages.
- Uncertainties inherent in the underlying system are represented in the OMs and may be related to the biology of the stock, the dynamics of the fleet, the observation process, and the implementation process. Estimates of commercial catches are considered reliable since 1996 for trawl-caught groundfish (due to 100% at-sea observer coverage) and since 2006 for line-caught species (due to 100% electronic monitoring).
- The framework provides a standardized and transparent approach across stocks, and should result in the provision of evidence-based catch advice for more stocks than at present.
This Science Advisory Report is from the June 8-9, 2020 meeting on A Management Procedure Framework for British Columbia Groundfish. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.
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