Genetic management of mixed-stock fisheries real-time: The case of the largest remaining cod fishery operating in the Atlantic in 2007-2017

Fish stocks represent fundamental units in fisheries management, and their identification, especially in mixedfisheries, represents one of the primary challenges to sustainable harvest. Here, we describe the first real-time genetic management program used to manage a mixed-stock fishery of a non-salmonid and commercially significant marine fish, the Atlantic cod (Gadus morhua L). Based upon the analysis of > 18 000 fish sampled from the commercial catch in Lofoten (Norway), which represents the largest remaining cod fishery in the Atlantic, we estimated the fraction of North East Arctic cod (NEAC), and Norwegian Coastal cod (NCC), just 24 h postlanding. These estimates, based upon the analysis of the Pantophysin gene, were performed weekly in the winter and spring of each year in the period 2007-2017. The program has successfully permitted the Norwegian Directorate of Fisheries to actively manage the commercial exploitation of the highly abundant NEAC stock, while simultaneously limiting exploitation of the fragile NCC stock, both of which overlap at the spawning grounds. Data from this program have also revealed a distinct temporal increase in the fraction of NEAC on the spawning grounds in this region, which is consistent with the overall increased abundance of this stock as estimated by ICES.