Abstract
Fish stocks represent fundamental units in fisheries management, and their identification, especially in mixed-fisheries, 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 post-landing. 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.
Highlights
Harvest from the world’s oceans has remained stable between 80–90 million tonnes/annum since the mid-1980s, and many of the world’s fisheries are either fully or over-exploited, depleted, or recovering from depletion (FAO, 2016)
Mixed stock fisheries may occur where separate populations partially or completely overlap in their spawning areas. This is for example the case for the Northeast Atlantic cod (Gadus morhua) (NEAC) and Norwegian coastal cod (NCC) which have and continue to form the basis of major fisheries along the coast of Norway, and especially the Lofoten Islands (Fig. 1)
Depending on the year and exact location sampled, in general, the fraction of North East Arctic cod (NEAC) in the commercial catch increased during the period February–March, peaked in the period late March early April, and decreased thereafter (Fig. 2)
Summary
Harvest from the world’s oceans has remained stable between 80–90 million tonnes/annum since the mid-1980s, and many of the world’s fisheries are either fully or over-exploited, depleted, or recovering from depletion (FAO, 2016). Mixed stock fisheries may occur where separate populations partially or completely overlap in their spawning areas This is for example the case for the Northeast Atlantic cod (Gadus morhua) (NEAC) and Norwegian coastal cod (NCC) which have and continue to form the basis of major fisheries along the coast of Norway, and especially the Lofoten Islands (Fig. 1). In 2005, the Institute of Marine Research (IMR) conducted a pilot study in Lofoten to evaluate the logistical feasibility of genotyping the PanI locus to estimate the fractions of NEAC and NCC from commercial landings in this economically important fishery “real-time” – i.e., within 24 h post-sampling Based upon this pilot study, a genetics-based fishery program was established in cooperation with the Norwegian Directorate of Fisheries (NDF) to control the annual fishery in this area in the late winter and early spring. We present the results of this fisheries regulation program that has run annually in the period 2007–2017 and includes the weekly-estimation of NEAC fraction in the commercial catch in 200 independent samples based upon the analysis of the PanI locus in > 18 000 cod
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