Science Advisory Report 2021/004

Science Advice for Precautionary Approach Harvest Strategies under the Fish Stocks Provisions

Summary

• This Science Advisory Report (SAR) provides advice to the Science Sector concerning the implications of the revised Fisheries Act (2019), particularly the Fish Stocks provisions (FSP). The FSP are viewed in light of Canada’s Fishery Decision-Making Framework Incorporating the Precautionary Approach (the ‘PA Policy’). The advice is organized into sections according to the text of the new legislation. Key points selected from the recommendations in the body of this report appear below.

“Major fish stocks” in the context of the “limit reference point”

• A single limit reference point (LRP) may be required for those major fish stocks prescribed under the FSP, but at present it is not always the case that major stocks have a single LRP due to varying degrees of disaggregation of stock subunits.
• There is a need to consider the role of LRPs relative to three scenarios (i.e., the spatial distribution of the stock is the same as that of the biological unit, the stock (subunit) is smaller than the biological unit, and stock is larger than the biological unit).
• There is a need for Science guidelines to address situations where scale mismatch between the stock definition, LRP choice, and data collection may reduce effectiveness of management measures with respect to desired outcomes, as well as a need to identify approaches to resolving such effects.

“The level necessary to promote sustainability of the stock”

• Definitions of sustainability and related terms generally recognize both time (i.e., some state that is achieved or sustained over the long-term) and the need for equitable availability of benefits across generations of resource users. Both considerations are consistent with the precautionary approach and the PA Policy.
• Promoting sustainability based solely on consideration of biological elements would prioritize management objectives related to conservation alone, at the expense of considerations of resource use. Without targets or thresholds and management measures it is not possible to operationalize sustainability in ways that reflect not only conservation, but also socio-economic, cultural, or other objectives for the stock and dependent fisheries.
• A definition of a level necessary to promote sustainability of the stock is suggested as “a threshold representing a specified level of practical and effective resource use over the long term.” This threshold, set below a higher target, must be above the LRP to be consistent with promoting stock sustainability.
• Thresholds representing a “level necessary to promote sustainability of the stock” in s 6.1(1) and lower levels that still enable a stock to be maintained acceptably above the LRP in s 6.1(2) differ as a result of trade-offs among conservation, socio-economic and cultural outcomes for the stock and fisheries.
• Fish stocks could be evaluated under the FSP using a composite performance measure of sustainability based on elements of the PA Policy. Evaluation would consider whether a stock is within limits (i.e., status exceeds the LRP and falls below a limiting fishing mortality rate represented by the Removal Reference (RR) in the PA Policy). Evaluation would also consider whether management measures perform acceptably with respect to avoiding limits and achieving targets over specified time frames.

“…Taking into account the biology of the fish and environmental conditions affecting the stock”

• There is a need to take into account a range of life histories, data availability and understanding of stock biology and environmental conditions in providing science advice. Science guidelines are needed to help the Science Sector:
• communicate how biological and environmental considerations are reflected in analyses and alternative hypotheses about stock dynamics;
• document what considerations were explored, and the rationales for their inclusion in advice, or explanations of why such linkages could not be demonstrated;
• demonstrate how such considerations can be incorporated by providing science advice on management measures that aim to be robust to a range of plausible stock and fishery dynamics related to environmental considerations.

Status relative to “the limit reference point”

• Science guidelines should establish consistency in the way that stock status is determined and reported relative to the LRP, with respect to uncertainty and time. Where status determination has invoked the need for a rebuilding plan under s 6.2(1), consistency in the way stock status is determined and reported relative to an agreed upon rebuilt state should similarly be established.

“Minimizing further decline of the fish stock”

• Science guidelines for developing rebuilding strategies should describe the means by which alternative management measures can be evaluated with respect to defined management objectives and associated performance measures.
• Such evaluations can provide support for amendments to rebuilding plans under s 6.2(2) that could meet the legal obligation to minimize further decline of the stock, and the PA Policy intent of “no tolerance for preventable decline” when a stock is below a LRP.

“If… the loss or degradation of the stock’s fish habitat has contributed to the stock’s decline”

• As for the consideration of environmental conditions, it is recommended that science guidelines be developed that should address how to:
• communicate habitat considerations;
• link such information to hypotheses for stock response (documenting rationales for inclusion in advice, or explanations of why such linkages could not be demonstrated);
• demonstrate how such considerations can be incorporated into science advice; and
• advise on the likely tradeoffs that result from alternative habitat restoration measures.

Implementation Needs for Science

• Science guidelines should address the roles of limit, threshold and target reference points, and address how these may be expressed as biomass or fishing mortality metrics (or suitable alternatives) for a range of life histories and data/model availability.
• Science guidelines can distinguish reference points from management measures (e.g., operational control points in harvest control rules (HCRs)), and identify how different management measures that may include HCRs can be evaluated with respect to objectives concerning limits, thresholds and targets.
• There is a need for methods to meet PA Policy intent for data-poor contexts where it may not be possible to reliably determine reference points, stock status or whether fishing at rates above a limiting rate (overfishing) is occurring.
• International comparisons suggest that limit fishing mortality rates need not be segmented to vary with stock abundance. PA Policy intent can still be met by application of management measures that reduce fishing mortality rates as stocks decline in order to acceptably avoid LRP breaches. The Science Sector can report on stock status and evaluate management measures relative to limit fishing rates such as F_MSY or proxies, or suitable alternatives when available.
• Identification of the intended function(s) of the upper stock reference (USR) and RR in stock-specific contexts is needed to clarify science advice on the selection of management measures intended to meet specified objectives. Assigning the USR a role as a target or threshold reference point to be achieved, rather than its primary role in managing the risk of a LRP breach, means that distinguishing operational control points (in management measures) from reference points (in management objectives) is critical.
• It is recommended that the Science Sector engage in discussions with other DFO Sectors to clearly define the role of targets and thresholds in the context of conservation and sustainable resource use to ensure consistency of application across stocks, standardize reporting, and investigate the application of risk equivalency.

Roles and Responsibilities of the Science Sector

• Consistent with the PA Policy, the Science Sector establishes LRPs, and evaluates stock status against B- and F-based limit and target reference points whether based on maximum sustainable yield (or proxies), or alternatives.
• Science requirements for the implementation of s 6.1 can be interpreted as characterization of stock status, and support for the identification of effective management measures that aim to achieve thresholds that “promote the sustainability of the stock” (s 6.1.1) or lower levels that maintain stocks above the LRP (s 6.1.2).
• Reference points and the acceptable risks associated with failing to either achieve targets or thresholds, or avoid limits, over specified time frames are captured in fisheries management objectives. Objectives reflect value-based goals and cannot be established based solely on scientific considerations.

This Science Advisory Report is from the May 26-27 and June 22-23, 2020 national advisory meeting on Science Advice For Precautionary Approach Harvest Strategies under the Fish Stocks Provisions. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2021/004 (PDF, 882 KB)

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