Science Response 2015/005
Status of Cusk (Brosme brosme) in NAFO Divisions 4VWX5Z Under the Precautionary Approach Framework
Context
Cusk, Brosme brosme, is caught as bycatch in certain directed fisheries. Most landings are in the groundfish longline fisheries. Commercial catch rates for Cusk have declined since the 1980s. Changes to management measures (e.g., reductions to trip limits, overall caps, and bycatch percentages) may have contributed to this reduction in catch rates (and landings); however, it is thought the decline in catch per unit effort (CPUE) is also due to a decline in Cusk abundance (Harris and Hanke 2010). The extent of the decline in abundance is not known.
In 2003, Cusk was assessed as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). In response to the 2003 assessment, the Governor in Council decided in 2013 not to add Cusk to the List of Wildlife Species at Risk set out in Schedule 1 of the Species at Risk Act (SARA). In November 2012, however, Cusk was reassessed as Endangered by COSEWIC and is subsequently under re-consideration for listing pursuant to SARA despite the 2013 Governor in Council decision not to list.
Presently there is no dedicated survey to monitor Cusk abundance; however, the Industry-DFO Halibut Longline Survey (Halibut Survey) catch rate (kilograms per 1000 hooks) has been accepted as an index. A methodology for identifying reference points (Harris et al. 2012)., based on the 2009 DFO policy document “A fishery decision-making framework incorporating the Precautionary Approach” (PA Framework), was adopted in 2012 The average of the commercial longline CPUE from the period of higher catch rates (1986-1992) in the commercial fishery was used as a proxy for biomass at Maximum Sustainable Yield. The Upper Stock Reference (USR) and Limit Reference Point (LRP) for Cusk were set at a CPUE of 26.6 kg/1000 hooks and 13.3 kg/1000 hooks, respectively, in the Halibut Survey. The 3-year geometric mean was accepted as the metric for monitoring Cusk status relative to the USR and LRP. The stock’s status in relation to the reference points was subsequently reviewed in December 2013 as a stock status update for Cusk in NAFO Divisions 4VWX5Z (DFO 2014a).
The question posed to Science by DFO’s Resource Management Sector is “What is the three-year geometric mean of the Cusk CPUE from the Halibut Survey relative to the USR (26.6 kg/1000 hooks) and the LRP (13.3 kg/1000 hooks)?”. The information will be used by DFO Resource Management as guidance for discussions with various industry stakeholders on recommendations for management measures. In particular, the Science Response will be provided to industry at the Scotia-Fundy Groundfish Advisory Committee meeting during discussions on implementing the PA Framework.
The 3-year geometric mean (2012-2014) of the Cusk CPUE is 13.3 kg/1000 hooks, the lowest point since 2009, which suggests that the stock is at the LRP (Figure 1).
This Science Response Report results from the Science Response Process of December 12, 2014, on the 4VWX5 Cusk Stock Status Update.
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