Science Response 2017/028
Western Component (4Xopqrs5) Pollock Harvest Control Rule Update and Indicators Report
Context
Pollock (Pollachius pollachius) in Northwest Atlantic Fisheries Organization (NAFO) Areas 4VWX5 comprise two population components: a slower-growing Eastern Component including Divisions 4V and 4W, as well as Unit Areas 4Xm and 4Xn, and a faster-growing Western Component (WC) including 4Xopqrs and Canadian portions of Area 5. The WC has been the main focus of past analytical assessments, but scientific advice on stock status and catch limits using Virtual Population Analysis (VPA) modeling has been highly variable, especially since the mid-2000s. For example, the 2008 assessment indicated that Age 4+ population biomass was at 27,000 metric tonnes (mt) (Stone et al. 2009), while the 2010 assessment update indicated Age 4+ population biomass was either 23,000 mt or 17,000 mt, depending on whether the very low 2010 DFO Summer Research Vessel (RV) Survey indices were excluded or included in the analysis (Stone 2011). Consequently, the Canadian fishing industry recommended exploration of alternative approaches that would provide more stability in future catch limits to allow for better business planning and a more stable fishery.
In 2011, fisheries managers and the fishing industry decided to manage WC Pollock using a risk-management approach and embarked on a Management Strategy Evaluation (MSE) process, with the help of government scientists and outside experts (DFO 2011). MSE is a technique to explicitly consider the uncertainty in stock assessment assumptions and models, and to compare the likely consequences to Management Objectives when a predetermined Management Procedure (MP) incorporating a Harvest Control Rule (HCR) is applied. The Pollock MP was selected on the basis of satisfying three medium-term objectives agreed upon for management of the resource, which relate to sustainability, catch levels, and the extent of annual catch changes. The MP model was built around a HCR that either increased or decreased future catch limits based on results from ongoing monitoring from the annual DFO Summer RV survey. An Exceptional Circumstances Protocol was put in place to cover situations that fall outside the range for which the MP was simulation tested and, if necessary, to allow for some form of intervention.
Recently, Fisheries Management posed the following question to Science: What is the Western Component catch level for fishing year (FY) 2017/2018 generated by the HCR described in DFO 2011 “Western Component Pollock Management Strategy Evaluation”? This report provides an update to the 2015 report (DFO 2016) on the WC Pollock HCR and provides advice on the FY 2017/2018 catch limit generated by the Pollock MP and HCR using updated information from the 2016 DFO Summer RV survey. It also describes current status with respect to the provisions in the Exceptional Circumstances Protocol. The HCR, with updated monitoring data for 2016, generated a catch limit of 2,670 mt for FY 2017/2018 and up 20% from 2,225 mt for FY 2016/2017. The DFO Summer RV survey biomass index increased from 4.55 kg/tow in 2015 to 28.15 kg/tow in 2016 and, therefore, did not trigger the exceptional circumstance provision of the DFO Summer RV survey biomass index being < 6 kg/tow for two consecutive years and the Survey Index Ratio being < 0.2.
At the MSE framework in 2011, a full review of the Pollock MP and its HCR was proposed for 2016; however, at this time Fisheries Management and Industry requested a preliminary review of the HCR data inputs.This update report provides a review of additional indices of WC Pollock biomass from the U.S. National Marine Fisheries Service (NMFS) Spring and Fall surveys, and recent DFO Summer RV survey coverage of eastern Georges Bank. Applying updated DFO Summer RV survey data to the FY 2016/2017 Total Allowable Catch (TAC) was also examined. Updated information on commercial catch-at-age, fish condition, and mean lengths-at-age are also discussed.
This Science Response Report results from the Science Response Process of December 13, 2016, on the Stock Status Update of Western Component (4Xopqrs5) Pollock Harvest Control Rules.
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