Search

This paper presents an assessment modeling framework that integrates all available fishery monitoring and survey data into a Spatially Implicit Statistical Catch-At-Length (SISCAL) operating model for Northwest Atlantic Fishery Organization (NAFO) Subareas 0+1 (offshore) Greenland Halibut (GH-0+1). The model is subsequently used to provide both an assessment of stock status and productivity as well as a closed loop simulation framework for evaluating GH-0+1 feedback harvest strategies. The SISCAL model fit reasonably well to GH-0+1 data, as determined by standard goodness of fit metrics, although some sensitivities and data issues were noted. The retrospective behaviour of the model was also within reason. Simulationevaluation self-tests also showed that the model was unlikely to be biased over a large number of simulated data sets. After model testing, SISCAL was used to condition a closed-loop simulation framework for testing GH-0+1 management procedures against performance metrics based on NAFO precautionary approach fishery management policy. As an illustrative example, we defined an adaptive model/index-based management procedure that set total allowable catches on a biennial basis, using decision rule parameters that were updated via simulated SISCAL stock assessments every 6 years. Simulated SISCAL stock assessments were fit to historical and simulated catch and biological data from six commercial fleets, differing by nation and gear type, and stock indices and length compositions from three fishery independent surveys. The three surveys included two existing offshore (NAFO Divisions 0A1CD) and inshore (NAFO Divisions 1A to F) research vessel surveys, as well as an additional proposed survey that will begin in 2022 and was assumed to encounter small fish in inshore waters of Divisions 0A and 0B. For comparison, a non-adaptive index-based method was also tested, where decision rule parameters are based off the initial SISCAL model for the entire simulation. The adaptive procedure performed well, keeping biomass above the limit reference point of = 0.3BMSY in all simulations, and avoiding the limit fishing mortality rate Flim = FMSY with high probability. In contrast, the non-adaptive procedure ended up slightly overfishing the GH-0+1 stock, with biomass appearing to continue declining past the end of the simulation. Moreover, the non-adaptive procedure had a roughly neutral probability of exceeding Flim, making it unacceptable under NAFO policy. We close with recommendations for future work to expand this framework to a full management strategy evaluation, enabling the development of a full harvest strategy for the GH-0+1 fishery consistent with fishery management policy. [ABSTRACT FROM AUTHOR]

Atlantic Herring (Clupea harengus) in Northwest Atlantic Fisheries Organization (NAFO) Division 4T, referred to as the southern Gulf of St. Lawrence (sGSL), consists of two spawning components, spring spawners and fall spawners. This document presents the most recent information on trends in abundance, distribution, and harvest for the spring and fall spawning Herring components in NAFO Division 4T. This includes catch-at-age and catch-per-unit-effort (CPUE) indices, fisheries-independent acoustic indices, experimental gillnet survey indices, mesh selectivity, fishery-dependent acoustic indices and catches in the multi-species bottom trawl survey of the sGSL. The data and indices are reported for the sGSL for the spring spawners, and regionally-disaggregated (North, Middle, and South regions) for the fall spawners where applicable. Spring spawners were assessed using a statistical catch at age (SCA) model that allowed for time-varying catchability to the gillnet fishery and time-varying natural mortality. The model estimated that spawning stock biomass (SSB) has been in the critical zone of the Precautionary Approach framework since 2002. The SSB median estimate in April 1 2022 is estimated to be 28,835 tons (t); 62% of the limit reference point (LRP = 46,340 t). Under current low recruitment and high natural mortality conditions, this stock is not expected to recover in the short or the long term. Reducing fishing mortality will have marginal effects on the projected SSB trends. By 2027, the probability of exceeding the LRP was not more than 20% at all catch levels, with SSB values ranging between 32,500 and 35,400 t. Fall spawners were assessed as regionally-disaggregated populations using a SCA model that allowed for time-varying catchability to the gillnet fishery and time-varying natural mortality. Estimated SSB has been declining in all three regions in recent years and is currently in the Cautious Zone of the Precautionary Approach framework. At the target catch level in 2021 (~12,000 t), the probabilities of a 5% increase in SSB by 2024 are all under 40%. Long-term projections show a continuous decline of SSB, however the probability of moving into the Critical Zone (under the LRP) by 2027 was 0% at all catch levels. As a consequence of low productivity and high natural mortality, exploitation of this stock should assert caution until high recruitment is observed for consecutive years. [ABSTRACT FROM AUTHOR]

The status of the northern contingent of Atlantic mackerel (Scomber scombrus) in the Northwest Atlantic is assessed every two years using an age-structured stock assessment model. This document presents the background information, data, and methods used to calculate the main stock status indicators for mackerel which form the basis of advice given to the Fisheries and Aquaculture Management Branch of Fisheries and Oceans Canada (DFO) in the setting of Total Allowable Catch (TAC). The present stock assessment took place on the 25-26 of February and March 3rd of 2021 and provides advice for the 2021-2022 fishing seasons. The main results of this assessment indicated that in 2020, the spawning stock biomass (SSB) of mackerel was estimated to be at an all-time low and in the Critical Zone, as per DFO's Precautionary Approach (PA), since 2011. Recruitment of age 1 fish was estimated to be near record lows in recent years and the age structure of the stock was severely truncated. The fishing mortality rate (F) was also above the reference point. Short-term projections indicated that the probability of the SSB leaving the Critical Zone by 2023 varied from 29%-37% (TAC = 10 000 t) to 51%-58% (TAC = 0 t) depending on the assumptions of future recruitment. [ABSTRACT FROM AUTHOR]

Canada's Fisheries Act was revised on June 21, 2019, resulting in new Considerations and Fish Stocks provisions (FSP) that relate to the management of fisheries. The FSP (Section 6) contains new terminology: 1) a requirement to implement measures to maintain major fish stocks "at or above the level necessary to promote the sustainability of the stock" (s 6.1(1)); and 2) if those management measures are unfeasible due to cultural or socio-economic impacts, to maintain stocks above the limit reference point or LRP (s 6.1(2)), which is a biological threshold to serious harm. Definitions of sustainability recognize both time and the need for equitable access to benefits across generations of resource users. Most jurisdictions recognize multiple axes of sustainability including ecological, socio-economic and institutional axes, but prioritize them differently. Consideration of all axes is necessary to operationalize fisheries management to support sustainable use, and science alone cannot advise on all of them. A pragmatic definition of sustainability in fisheries is that it is the process that conveys the ability to maintain a specified level of practical and effective use of a fisheries resource over the long term, where practical and effective reflects value-based measureable objectives related to biological, socio-economic and cultural outcomes. In the same vein, a level necessary to promote sustainability of the stock can be defined as "a threshold representing a specified level of practical and effective resource use over the long term." In the absence of clearly-defined value-based objectives for resource use or tolerance for risk to the stock, the threshold cannot be defined more specifically. Thresholds and other levels fulfilling s 6.1(1) or s 6.1(2) differ with respect to trade-offs among biological, socio-economic, and/or cultural objectives but both sections imply the stock be maintained above the LRP. Limits, other thresholds and target reference points play important roles in constraining which stock states are considered sustainable internationally. Review of Canada's PA Policy suggests that fisheries sustainability could be evaluated, in part, by considering whether stock status exceeds the LRP and whether fishing mortality is less than the removal reference rate. The question of sustainability can also be assessed by evaluating whether management measures are expected to perform acceptably with respect to stated limits and targets over specified time frames. The multiple axes of sustainability imply there is a role for multiple sectors in defining and promoting stock and fisheries sustainability. The Science Sector sets LRPs, evaluates stock status against reference points, and may contribute by evaluating other elements of the ecological axis of sustainability such as age or size composition of the stock, habitat, trophic level and other ecosystem considerations in relation to objectives. Setting targets, other thresholds, time frames and determining acceptable risks are value-based choices and cannot be established via scientific means alone. All Sectors may benefit from Departmental guidance as to how s 6.1(1) and s 6.1(2) differ in implementation, particularly with respect to the use of PA Policy reference points in management objectives, and implications for management measures including harvest control rules. [ABSTRACT FROM AUTHOR]

Canada's Fisheries Act was revised in 2019 to include new Fish Stocks provisions. Updated science guidelines to support the Sustainable Fisheries Framework policies, in particular the Fishery Decision-Making Framework Incorporating the Precautionary Approach (PA Policy), and legal and regulatory requirements are also under development. To inform the development of science guidelines, we reviewed the technical specifications of reference points and harvest control rules for a subset of key harvested stocks, focusing primarily on those domestically managed and subject to the PA Policy. The adoption of default guidance values of the limit reference point (LRP) and upper stock reference (USR) provided in the PA Policy (0.4 and 0.8 BMSY) is not required, but these values appear to have been widely embraced (43% and 65% of cases, respectively). The USR by definition serves a number of functions, including an operational control point (trigger for management action) to control the risk of approaching the LRP, Healthy-Cautious zone boundary, and target. Science guidelines can provide support for identifying alternative USRs by noting proxies for BMSY (enabling use of proxies for 0.8 BMSY) and by addressing various functions attributed to the USR separately. Removal References (RRs), like USRs, may serve multiple purposes across the stocks in this review. We found that RR values are consistent with indicating whether harvests are at "approved [target] levels" in a wide range of stocks, and sometimes with limits to be either avoided or with which to characterize acceptable stock status in terms of overfishing on the fishing mortality (F)-axis of the PA Policy. Science guidelines could provide support for identifying RRs by highlighting FMSY proxies and characterization of stock states on the F-axis. Four broad types of harvest control rules (HCRs) appear to be implemented in Canada: feedback status-based rules, mixed feedback/feed-forward risk-based rules, "constant" rules with no operational control points and feedforward-only objective-based "rules." The provisional HCR suggested in the PA Policy guidance is not often used although three-part rules with control points at the LRP and USR are common (38% of HCRs). Rules varied widely, although the vast majority are targeted toward informing quantitative output controls (catch limits). To support the new provisions, the development of updated science guidelines should aim to support easier identification of PA components and more consistent use of terminology for key aspects of the PA Policy, including reference points, operational control points for HCRs, and measurable objectives. The HCR types and other measures will vary widely for fisheries that represent a spectrum of data and assessment model availability for key harvested stocks. As science support may be requested for developing and evaluating a wide range of HCRs, science guidelines will need to address both prospective and retrospective evaluation for an array of possible rules that reflect input and output controls and interact with other management measures. [ABSTRACT FROM AUTHOR]

Rebuilding plans are required by law under the new Fish Stocks provisions of the revised Fisheries Act for major fish stocks prescribed under regulations that have declined to, or below, their limit reference point. The provisions state that the biology of the fish and environmental conditions facing the stock will be taken into consideration in the design of rebuilding strategies. Rebuilding strategies inform the development of rebuilding plans and should be regarded as integral to overall management (harvest) strategies. Science activities focus on the development and evaluation of management strategies in response to stated objectives, including rebuilding. Viewing a rebuilding strategy as separate from the overall management strategy can lead to the deferral of actions intended to prevent stock decline. Failure to plan rebuilding measures before they are needed can create hard-to-resolve conflicts with measures intended to provide opportunities for resource use. Increased likelihood that rebuilding is achieved depends on planning the transition from rebuilding to target outcomes within a management strategy. Like many other jurisdictions, Canada advocates management by reference points. Our review of international fisheries agreements highlights key elements that produced Canadian fisheries policy related to the Precautionary Approach. Interpretation of policy must distinguish between objectives that embed biological reference points related to abundance or fishing mortality, and the management measures intended to provide acceptable stock and fishery outcomes. As management by reference points can be challenging when there is data- or model-poverty, rebuilding strategies for such stocks should prioritize increasing information needed to adapt the rebuilding plan while preserving policy intent to avoid or correct undesirable stock states. We review obligations for recovery strategies under the Species at Risk Act and an ecocertification standard to evaluate where common information demands exist that could lead to efficiencies in providing advice. Existing Canadian rebuilding plans are reviewed to identify information needed to support rebuilding considerations in light of proposed regulations to support the Fish Stocks provisions. We discuss components of rebuilding strategies needed to meet proposed regulations. These include determining when rebuilding is needed, identifying the rebuilt state, and specifying a time period over which to implement a rebuilding plan. One science role is consistent communication of the plausible range of stock scenarios during the lifespan of the plan to inform expectations of decision-makers and resource users. Plan success can be enhanced by allowing for adaptation during the rebuilding period as new data, updated analyses, and revised objectives are considered. We suggest principles for developing national science guidelines for rebuilding fish stocks. Guidelines are intended to clarify expectations for, and to encourage, consistent science practices. We advocate a structured decision-making approach to developing feasible rebuilding strategies, identifying possible scenarios and eliciting objectives from resource users and decision-makers. The process can be used for data-poor contexts and maps directly into quantitative approaches such as management strategy evaluation. Finally, we provide a recommended list of elements for rebuilding strategies that should be reflected in science guidelines. [ABSTRACT FROM AUTHOR]

Atlantic Herring in the southern Gulf of St. Lawrence (sGSL) consists of two spawning components: spring spawners and fall spawners. This document presents the most recent information on trends in abundance, distribution, and harvest for the spring and fall spawning Herring components in NAFO Division 4T. This includes catch-at-age and catch-per-unit-effort (CPUE) indices, fisheries-independent acoustic indices, experimental gillnet survey indices, mesh selectivity, and catches in the multi-species bottom trawl survey of the sGSL. The data and indices are reported for the whole-area for the spring spawners, and regionallydisaggregated (North, Middle, and South regions) for the fall spawners where applicable. Spring spawners were assessed using a statistical catch at age (SCA) model that allowed for time-varying catchability to the gillnet fishery and time-varying natural mortality. The model estimated that spawning stock biomass (SSB) has been in the critical zone of the Precautionary Approach framework since 2002. The SSB median estimate in April 1 2020 is estimated to be approximately 26,000 t; 55 % of the limit reference point (LRP = 47,250 t). Under current low recruitment and high natural mortality conditions, this stock is not expected to recover in the short or the long term. Reducing fishing mortality only slightly reduces the probabilities of SSB decline in projections. By 2029, the probability of exceeding the LRP was 0 % at all catch levels, with SSB values ranging between 160 and 1,198 t. Fall spawners were assessed as regionally-disaggregated populations using a SCA model that allowed for time-varying catchability to the gillnet fishery and time-varying natural mortality. Estimated SSB has been declining in all three regions in recent years and is currently in the Cautious Zone of the Precautionary Approach framework. At the target catch level in 2019 (16,000 t), the probabilities of a 5 % increase in SSB by 2022 are 29 %. Long-term projections show a continuous decline, with SSB in the Critical Zone by 2025. As a consequence of low productivity and high natural mortality, exploitation of this stock should assert caution until high recruitment is observed for consecutive years. The catch level offering the greatest probabilities of increasing SSB in the short and long term was 2,000 t. [ABSTRACT FROM AUTHOR]