Science response: evaluation of upper stock reference point options for Pacific herring

Pacific Herring (Clupea pallasii) in British Columbia (BC) are currently managed in five major and two minor stock assessment regions (SARs), and independent catch and survey information is collected for each area in order to provide annual science advice on this scale. The major SARs are Haida Gwaii (HG), Prince Rupert District (PRD), Central Coast (CC), Strait of Georgia (SoG), and West Coast of Vancouver Island (WCVI), and the minor SARs are Area 27 and Area 2 West. Pacific Herring have extensive annual time series of fishery-independent survey and biological sampling data extending back to 1950. With these data sources, Science, Pacific Region developed an annual stock assessment program and forecasting models, contributing to leading-edge research and development in fisheries science. Fixed harvest rates and simulation-tested harvest rules were adopted by DFO for the management of Pacific Herring in 1986, with rules prescribing an exploitation rate of 0% when predicted biomass fell below commercial cut-off levels (Hall et al. 1988). Since adopting the harvest strategy in 1986, two major herring stocks - SoG and PRD have remained above the cut-off level while major stocks in HG, CC, and WCVI experienced recent low biomass states that fell below cut-off levels. Observations such as declining biomass trends in the absence of commercial harvest, long-term declines in body size (weight-at-age), and an increasing trend in the estimated natural mortality rates spurred initiation of a management strategy evaluation (MSE) process in 2015 where the initial focus was on improving the understanding of the harvest control rule (HCR) performance against conservation objectives and identifying HCR choices that do not meet conservation objectives. Since 2015, Science, Pacific Region has established a MSE process (DFO 2015, DFO 2019a, DFO 2020), established limit reference points (Kronlund et al. 2018) and a core set of measurable objectives (DFO 2020a), and used feedback simulation-evaluation to provide advice on stock-specific harvest rates and HCRs (DFO 2019a, DFO 2020). Additionally, the MSE framework has been used to develop a rebuilding plan for HG herring1, demonstrating use of feedback simulation-evaluation as a foundation for developing rebuilding plans and meeting the Precautionary Approach (PA) Policy. DFO’s “A Fishery Decision-Making Framework Incorporating the Precautionary Approach” policy (DFO 2009), hereafter called the PA Policy, describes requirements for incorporating the precautionary approach for fish stocks in Canada. These requirements are summarized into four elements2: PA1. Establish limit and upper stock status reference points that delineate critical, cautious and healthy zones as well as a maximum fishing mortality rate; PA2. A harvest strategy and harvest control rules (HCRs, Kronlund et al. 2014a); PA3. Account for uncertainty and risk when developing reference points and when developing and implementing control rules (Kronlund et al. 2014a, b); and PA4. Evaluate the performance of the management system against the objectives specified by the harvest strategy (Kronlund et al. 2014b). To ensure consistency with the Sustainable Fisheries Framework and implementation of the PA Policy to Pacific Herring, Fisheries and Oceans Canada (DFO) implemented a spawning biomass-based limit reference point (LRP) of 0.3SB0 (unfished spawning biomass) for all five major stocks beginning in 2018 (Kronlund et al. 2018, DFO 2019b). The current management framework for Pacific Herring already has many of the required elements of the PA Policy, including LRPs (PA1), management procedures (MPs) designed to avoid the LRP with high probability (PA2, PA3), and evaluation of performance via simulation-evaluation (PA4, Cleary et al. 2019). Although candidate upper stock reference (USR) points were considered by Cleary et al. (2019), implementing a USR for each major stock is required to fully align Pacific Herring with the PA Policy. Options for establishing an USR for each SAR are described here with elements PA2, PA3 and PA4 already reflected in the management strategy evaluation (MSE) process first initiated in 2015 (DFO 2015). The new Fish Stock provisions of the revised Fisheries Act (R.S.C., 1985, c. F-14) passed into legislation in 2019. It introduced requirements to maintain major fish stocks at sustainable levels and to develop and implement rebuilding plans for stocks that have declined below the LRP. This legislation is relevant to the Haida Gwaii major stock area which was among the first ‘batch’ of stocks prescribed in regulation in 2022. The HG stock has persisted in a low biomass, low productivity state (Kronlund et al. 2018) from approximately 2000 to 2018, and has fluctuated at or below the LRP in most years since 2000 (DFO 2021b). As such, a draft rebuilding plan1 for Haida Gwaii Herring has been developed through a technical working group which includes representatives from the Council of the Haida Nation, DFO, and Parks Canada. Consultations on this rebuilding plan will commence in fall 2022. The purpose of this work is to describe the role of the USR for Pacific Herring, document and evaluate USR options, and describe criteria for selecting USRs for major SARs. Evaluation of the consequences of USR choice must be considered in the context of the entire management system. Thus, our analyses includes simulation-evaluation to examine the probability of meeting USR options under different management procedures. The simulations incorporate updates to operating model conditioning data and updated MPs for four of the major Pacific Herring SARs (PRD, CC, SoG, and WCVI). Simulation updates are not included for the Haida Gwaii major stock area because these analyses and updates are included in the rebuilding plan2. This Science Response Report results from the regional peer review of August 30, 2022 on the Management Strategy Evaluation Update and Evaluation of Upper Stock Reference Point Options for Pacific Herring (Clupea pallasii) in British Columbia, Canada.

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