Recent recovery and future prospects of the northeast Atlantic halibut stock

Atlantic halibut (Hippoglossus hippoglossus) has been commercially exploited in the northeast Atlantic Ocean for at least two centuries, but today the Norwegian fishery is the only remaining targeted commercial halibut fishery. The regulation of the Atlantic halibut fishery in Norway is divided between two management units along the Norwegian coast, north and south of 62°N. Here we tell the story of the largest and most economically significant Norwegian halibut population north of 62°N. The status of the stock was for the first time assessed, using an index of relative abundance derived with a model-based approach from survey data for a non-target species using reconstructed historic landings to inform a Stochastic Surplus Production model in Continuous Time (SPiCT). Our analyses reveal a stock that has recovered from depletion and now again sustains a significant fishery. However, recent landings have reached a level that raises concerns about the sustainability of the fishery. We provide suggestions on how this long-lived species may be assessed and managed to avoid stock collapse. Our approach of using non-targeted survey data to enable an analytical stock assessment with SPiCT may translate to other recovering Atlantic halibut stocks as well as other data-limited to data-moderate long-lived stocks.