Fish harvesting advice under climate change: A risk-equivalent empirical approach

RESEARCH ARTICLE Fish harvesting advice under climate change: A risk-equivalent empirical approach Daniel E. DupliseaID1*, Marie-Julie Roux1, Karen L. Hunter2, Jake Rice3 1 Fisheries and Oceans Canada, Institut Maurice-Lamontagne, Mont-Joli, QC, Canada, 2 Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, BC, Canada, 3 Fisheries and Oceans Canada, National Headquarters, Ottawa, ON, Canada * Daniel.Duplisea@dfo-mpo.gc.ca Abstract The rate of climate change (CC) has accelerated to the point where it now affects the mid- to long-term sustainability of fishing strategies. Therefore, it is important to consider practical and effective ways to incorporate CC into fisheries advice so that the advice can be consid- ered conditioned to CC. We developed a model to characterise the empirical relationship between a variable affected by climate and fish production. We then used model projections as a foundation for a risk analysis of CC effects on harvesting of Greenland halibut Rein- hardtius hippoglossoides in the Gulf of St Lawrence, Canada. The risk-based approach quantified a) the relative change in risk of a status quo fishing strategy under various CC scenarios, and b) the change in fishery exploitation rates required to achieve a management objective over a specified time period at a level of risk considered acceptable (risk equivalent fishery exploitation advice). This empirical approach can be used to develop risk-based advice for any other external variable that affects stock production in addition to climate-

related variables and it can be applied in most situations where there is an index of stock bio- mass and fisheries catch. Shifting the focus from process-based understanding of the responses of fish stocks to CC to quantification of how CC-contributed uncertainty can alter the risks associated with different fishing strategies and/or management options, can ensure timely delivery of robust scientific advice for fisheries under non-stationary environmental conditions. 1 Introduction Scientific advice for fisheries management typically comprises three steps: a) evaluating the present state of a fish stock, b) determining the impact of different levels of fishery removals on the stock relative to objectives specified in longer-term policies, and c) providing probabili- ties of achieving those objectives for each catch level. This approach has many assumptions, one of the most important is usually that the environment in which the fish stock occurs will be constant, or vary randomly without trend, over the period covered by steps b and c: the environmental conditions that are assumed for the objectives and those encountered during the projections to quantify impacts of removals. Climate change (CC), however, is a directional PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0239503 February 19, 2021 1 / 22 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Duplisea DE, Roux M-J, Hunter KL, Rice J (2021) Fish harvesting advice under climate change: A risk-equivalent empirical approach. PLoS ONE 16(2): e0239503. https://doi.org/

10.1371/journal.pone.0239503 Editor: Andrea Belgrano, Swedish University of Agricultural Sciences and Swedish Institute for the Marine Environment, University of Gothenburg, SWEDEN Received: September 3, 2020 Accepted: January 26, 2021 Published: February 19, 2021 Copyright: © 2021 Duplisea et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: Data are available through GitHub: www.github.com/duplisea/ccca. Funding: Funding for this work comes direct from The budget of the Treasury Board of Canada as the core budget of the Department of Fisheries and Oceans (DFO) and is known internally as ‘A-base’. A-base money supported salaries, travel, equipment of the four authors who are all employees of the DFO. Subsequent funding (~5 k CAD) from a specific departmental program