Science Response 2020/025
Evaluating the Robustness of Canditate Management Procedures in the BC Sablefish (Anoplopoma fimbria) Fishery for 2019-2020
Context
Since 2008, Fisheries and Oceans Canada (DFO) and the British Columbia (BC) groundfish fishing industry have collaborated on a management strategy evaluation (MSE) process intended to maintain a transparent and sustainable harvest strategy for Sablefish fisheries in BC. Transparency and potential sustainability of candidate management procedures (MPs) are demonstrated by simulating MP performance against a set of pre-agreed biological and fishery objectives (hereafter referred to as Fishery Objectives). Operating models underlying the simulations are intended to represent key uncertainties related to Sablefish stock status and productivity. The Sablefish MSE process has been reviewed in several Canadian Science Advisory Secretariat (CSAS) peer-review processes, and independent peer-reviewed scientific literature (Cox and Kronlund 2008; Cox et al. 2011, 2013, 2019; DFO 2014). Canadian Sablefish harvest advice derived from simulation-tested MPs has been adopted by DFO every year since 2011.
The Sablefish MSE aims to follow a 3-year cycle in which the operating model (OM) is re-fitted to updated fishery and survey biomass indices, catch-at-age, at-sea releases, and tag release recoveries. Each 3-year update also offers an opportunity to revise the Fishery Objectives, as well as to propose new candidate MPs.
Previous BC Sablefish assessments and MSE work have demonstrated that low recruitment (on average) over the past three decades has contributed to a long-term decline in spawning stock biomass and harvest opportunities. Stakeholder and management consultations identified at-sea release mortality of sub-legal Sablefish (i.e., fish smaller than 55 cm size limit) as a potential source of mortality that, if reduced or avoided, may improve production of over-55 cm Sablefish, spawning stock biomass, and, ultimately, future harvest opportunities (Cox et al. 2019). While some voluntary tactics aimed at reducing sub-legal mortality have been identified (e.g., improved fleet communication, and increased electronic monitoring), management measured aimed at reducing sub-legal mortality have not been formally evaluated through the Sablefish MSE process. However, past closed-loop simulations suggest that both full avoidance and full retention of sublegal Sablefish may improve both average annual Sablefish yield in directed fisheries as well as the probability of stock rebuilding to BMSY (Cox et al. 2011, 2019). Unfortunately, full avoidance may not be feasible, especially in trawl fisheries, which encounter sub-legal Sablefish as part of fishing operations for other species, while full retention may involve lost fishing opportunities (particularly for the trawl sector) and lower profitability for directed fisheries, because sub-legal Sablefish are worth less per-kilogram than legal-sized fish. In consultations, industry stakeholders suggested that a potential solution would involve incentives that shift fishing behaviour toward higher avoidance of sub-legal Sablefish.
The DFO Fisheries Management Branch has, therefore, requested that the Science Branch (i) update the Sablefish OM to include the most recent data available (up to 2018); (ii) update advice about expected performance of the current MP; and (iii) evaluate alternative MP and/or management measures aimed at reducing productivity losses to sub-legal mortality. The key issue in (iii) is identifying MPs that minimize the impact of such measures on fishing opportunities in non-directed fisheries (i.e., trawl) where sub-legal Sablefish are captured incidentally.
Advice arising from this CSAS Science Response will be used to select a new MP for BC Sablefish for years 2020-2022 that is compliant with the DFO Sustainable Fisheries Framework and A Fishery Decision-making Framework Incorporating the Precautionary Approach policy (DFO 2009). In addition, this Science Response informs fishery managers and stakeholders about the fishery implications of limiting productivity losses due to sub-legal Sablefish releases at sea.
This Science Response Report results from the Science Response Process of September 2019 on evaluating the robustness of candidate management procedures in the BC Sablefish (Anoplopoma fimbria) fishery for 2019-2020.
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