Abstract
AbstractThe advent of novel genetic methods has made it possible to investigate population structure and connectivity in mobile marine fish species: knowledge of which is essential to ensure a sustainable fishery. Haddock (Melanogrammus aeglefinus) is a highly exploited marine teleost distributed along the coast and continental shelf on both sides of the North Atlantic Ocean. However, little is known about its population structure. Here, we present the first study using single-nucleotide polymorphism (SNP) markers to assess the genetic population structure of haddock at multiple geographic scales, from the trans-Atlantic to the local (fjord) level. Genotyping 138 SNP loci in 1329 individuals from 19 locations across the North Atlantic revealed three main genetic clusters, consisting of a Northwest Atlantic cluster, a Northeast Arctic cluster, and a Northeast Atlantic cluster. We also observed a genetically distinct fjord population and a pattern of isolation by distance in the Northeast Atlantic. Our results contrast with the current management regime for this species in the Northeast Atlantic, as we found structure within some management areas. The study adds to the growing recognition of population structuring in marine organisms in general, and fishes in particular, and is of clear relevance for the management of haddock in the Northeast Atlantic.
Highlights
A biologically based fisheries management regime does not always coincide with current management regimes, which are often based on factors such as administrative boundaries, oceanographic features, spatial distribution of fisheries, and the most important target species in the respective areas (Reiss et al, 2009; Kerr et al, 2017)
To select a practical and robust set of single-nucleotide polymorphism (SNP) for high-throughput genotyping, the dataset was stringently filtered with respect to number of SNPs per double digest RAD (ddRAD) locus, presence of repeats, and length of the flanking sequence (Supplementary Text)
A stringent final set of 231 ddRAD loci were selected for SNP assay design, and 167 SNPs were successfully designed for the MassARRAY iPLEX system (Supplementary Table S1)
Summary
A biologically based fisheries management regime does not always coincide with current management regimes, which are often based on factors such as administrative boundaries, oceanographic features, spatial distribution of fisheries, and the most important target species in the respective areas (Reiss et al, 2009; Kerr et al, 2017). Inconsistency between population structure and spatial management units may result in the overexploitation of specific population components, causing loss of local genetic diversity and depletion, or even extinction, of local populations, which may go undetected if managed as a single unit (Allendorf et al, 2008). Failing to identify existing population structuring can lead to over-harvesting of one or more separate stocks in a fishery (Hauser and Carvalho, 2008), potentially causing a collapse (Cadrin, 2020) as exemplified by the Atlantic cod (Gadus morhua) fisheries in Newfoundland In the Northwest Atlantic, haddock is distributed from Cape May, NJ, to the Strait of Belle Isle, north of Newfoundland (Bigelow and Schroeder, 1953) and fisheries statistical units are set by NAFO (North Atlantic Fisheries Organization), recognizing six haddock stocks (3LNO, 3Ps, 4TVW, 4X, 5Z, and 5Y)
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