Year-round genetic monitoring of mixed-stock fishery of Atlantic cod ( Gadus morhua ); implications for management

• Published in: ICES Journal of Marine Science
• Main Authors: Christensen, Helle Torp, Riget, Frank, Retzel, Anja, Nielsen, Erik Haar, Nielsen, Einar Eg, Hedeholm, Rasmus Berg
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: DNA; fisheries management; fishery; migration; mixed stocks; GREENLAND WATERS; POPULATION; MARINE; DISCRIMINATION; DIVERSITY; MOVEMENTS; DYNAMICS; GROWTH; LIFE; MARKERS; Greenland; atlantic cod; East Greenland; Gadus morhua; Iceland
• Online Access: https://pure.au.dk/portal/da/publications/yearround-genetic-monitoring-of-mixedstock-fishery-of-atlantic-cod-gadus-morhua-implications-for-management(9a3292ec-8925-45f8-8f15-5fb05561ede6).html; https://doi.org/10.1093/icesjms/fsac076

Mixed-stock fisheries pose a challenge for fisheries management recommendations and management, as mixed stocks can lead to unintentional over- or under-exploitation of stocks, with both short- and long-term biological and economic consequences. This study demonstrates practical application and implementation of year-round high-resolution genetic stock monitoring in management of mixed Atlantic cod (Gadus morhua) stocks in western Greenland. Using a panel of 96 high resolution gene-associated SNPs, we identified the stock of origin for four cod stocks in the two major inshore mixed-stock fisheries. Contribution of individual stocks was quantified to identify if fjord sections, times of year, and fish size, would allow a "clean fishery" with a minimal contribution of the depleted West Greenland Offshore (WGO) population. High level of mixing was identified with 50% of inshore catches originating from the inshore stock, 20% from the East Greenland/Iceland offshore stock, and 30% from the WGO stock. Although some spatiotemporal variation of stock proportions was identified, a practice allowing exclusively fishing a specific stock was not possible. Accordingly, we demonstrate the need to allocate catches at the biological stock level and show that application of high-resolution genetics is a reliable and necessary tool.