Science Response 2014/004
Western Component (4Xopqrs5) Pollock Harvest Control Rule Update.
Context
Pollock in 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 t (Stone et al. 2009) while the 2010 assessment update indicated 4+ population biomass was either 23,000 t or 17,000 t, depending on whether the very low 2010 DFO Research Vessel (RV) survey indices were excluded or included from the analysis (Stone 2011). Consequently, the Canadian fishing industry recommended exploration of alternative approaches which would provide more stability in future catch limits to allow for better business planning and a more stable fishery.
Recently, 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 which 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 which 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) 2014-2015 generated by the Harvest Control Rule described in SAR 2011/054 “Western Component Pollock Management Strategy Evaluation”? This report provides advice on the FY 2014-2015 catch limit generated by the Pollock MP and HCR using updated information from the 2013 summer RV survey and describes current status with respect to the provisions in the Exceptional Circumstances Protocol. The HCR with updated monitoring data generated a catch limit of 3,072 mt for FY 2014-2015, down 20% from 3,840 mt for FY 2013-2014. The RV survey biomass index increased from 5.28 kg/tow in 2012 to 23.45 kg/tow in 2013, and avoided triggering the exceptional circumstance provision of the RV survey biomass index being < 6 kg/tow for two consecutive years and the Survey Index Ratio being < 0.2.
This Science Response Report results from the Science Response Process of 9 December 2013 on the Western Component Pollock Harvest Control Rule Update Report.
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