Science Response 2018/022
Stock Status Update of Atlantic Halibut (Hippoglossus hippoglossus) on the Scotian Shelf and Southern Grand Banks in NAFO Divisions 3NOPs4VWX5Zc
Context
Atlantic Halibut (Hippoglossus hippoglossus) is the largest of the flatfishes and ranges widely over Canada's East Coast. The management unit definition, Northwest Atlantic Fisheries Organization (NAFO) Divisions 3NOPs4VWX5Zc, is based largely on tagging results that indicate that Atlantic Halibut move extensively throughout the Canadian North Atlantic with smaller fish moving further than larger fish.
The Atlantic Halibut fishery was unregulated until a Total Allowable Catch (TAC) was implemented in 1988 and a legal size limit (≥81 cm total length) was established in 1994. The Fisheries and Oceans Canada (DFO) Research Vessel (RV) Survey provides an index of abundance for incoming recruitment for the stock. An Industry-DFO Longline Halibut Survey (Fixed Station Halibut Survey) on the Scotian Shelf and southern Grand Banks (NAFO Divs. 3NOPs4VWX5Zc) was initiated in 1998 to provide an index of exploitable (≥81 cm total length) Atlantic Halibut on the Scotian Shelf and southern Grand Banks. A new assessment model and assessment procedures were adopted in November 2014 (Cox et al. 2016) to inform Resource Management of the status of the Halibut resource and to provide harvest level advice based on standardized catch rates from the Halibut Survey and stratified mean numbers-per-tow from the DFO Summer RV Survey (NAFO Divs. 4VWX). Science advice provided in December 2014, 2015 and 2016 used this new procedure (DFO 2015, 2017). In 2017, following the recommendations outlined in the 2014 Assessment Framework, a new Stratified Random Halibut Survey was initiated that extended the survey into areas and depths that were not well sampled by the Fixed Station Survey. This new Survey contains 15 strata, divided into 5 subareas, and three depth zones. One hundred and fifty stations (150) were randomly selected with allocations to strata proportional to their area. The Stratified Random Survey will not be used to generate science advice this year. To calibrate the Stratified Random Survey with the Fixed Station Survey, 100 Fixed Stations will continue to be fished for at least three years. These 100 stations were selected to provide index of abundance for the provision of science advice on Atlantic Halibut harvest level. The next Framework review is currently scheduled for 2019; however, the calibration period will not be complete by this time.
Resource Management asked Science to update and evaluate Atlantic Halibut abundance indicators, landings and fishing mortality estimated from tagging data. This response provides 2018-2019 TAC advice based on the Objectives and Harvest Strategy adopted at the Scotia-Fundy Groundfish Advisory Committee (SFGAC) meeting in March 2015.
This Science Response Report results from the Science Response Process of December 4, 2017, on the Stock Status Update of 3NOPs4VWX+5 Atlantic Halibut.
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