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Landings of Atlantic halibut (Hippoglossus hippoglossus) have increased significantly in later years. More fishing boats are joining the open-access fishery, with an ever-increasing number of fishing gear. The Atlantic halibut is also a popular tourist and recreational fishery target species. Atlantic halibut is a large, late-maturing flatfish with life history traits that make the stock sensitive to overfishing. The stock has a long history of exploitation, and historical fisheries show that increased landings over time have been followed by significant reductions in landings. The current regulations of the Norwegian Atlantic halibut fishery north of 62°N consist of input regulations (minimum catch size, no-catch periods, and fishing gear restrictions). Management authorities suggest new management actions to ensure a sustainable fishery of the Atlantic halibut stock in a long-term perspective. The aim of this study was to perform a stock assessment of the Norwegian Atlantic halibut stock north of 62°N using a data-limited approach. The purpose was to use the Stochastic Surplus Production Model in Continuous Time (SPiCT) and empirical approaches (with Data Limited Methods Toolkit (DLMtool)) on the limited data to assess the stock status and propose a management advice. The potential effects of tourist- and recreational fisheries were also examined through alternative landings (+20% and +40%) scenarios. Landings in Norway north of 62°N and Norwegian coastal scientific survey data were used. Four survey indices were developed from the scientific survey, of which one was used in the full assessment. The SPiCT assessment fulfilled the technical criteria, and the halibut stock was given ICES (International Council for the Exploration of the Sea) category 2 MSY (maximum sustainable yield) advice. The DLMtool gave similar results and provided estimates of a new minimum catch size. The assessment showed that the stock is close to optimal levels and utilized around MSY. The stock is probably declining due to overfishing in recent years. The management advice for the Norwegian halibut stock north of 62°N is to reduce fishing by implementing a TAC at 2000-2424 tons. An increased minimum catch size of around 90-106 cm should be implemented (together with or independently of other measures) to fit the species' life-history traits better. Tourist- and recreational fisheries might have a negative effect on the halibut stock, especially locally. The findings in this thesis can contribute to better management of the Norwegian halibut stock north of 62°N. |
