Abstract
Genetic variation at the genomic level is invaluable to identify fish stock structure in fisheries management. It has been widely accepted that populations of marine fishes are highly connected owing to fewer barriers to gene flow and increased connectivity resulting from greater dispersal abilities. Since population genomic approaches have increased the accessibility and resolution of population genetic data, it further facilitates to study and detect previously unidentified structures as well as signatures for natural selection in wild populations. In the present study, restriction-site associated DNA (RAD) sequencing was applied to the samples of genome-wide single nucleotide polymorphisms (SNPs) of Engraulis japonicus, a small pelagic fish of ecological and economic importance in the northwestern Pacific. To assess population genetic structure as well as detection for local adaptation of E. japonicus, a total of 389 individuals from six regional populations of the northwestern Pacific were collected and a set of 12,627 SNPs was developed. Marginal significant genetic structure (average FST value was approximately equal to 0.002) was detected between regional populations of “the Bohai Sea population (BHS)” and the “the Japan Sea population (JPS)” as well as between “the North Yellow Sea population (NYS)” and the “the Japan Sea population (JPS)”. Moreover, no sign of local adaptation was detected, which might be the product of high gene flow among regional populations. Overall, our results improve the understanding of fine-scale population genetic structure in E. japonicus and potentially identify management unit in this species area.
Highlights
Different fish stocks may respond differently to fluctuations of environmental factors as well as fishing pressures
Adaptive divergence is widely believed to be rare in marine fishes as compared to terrestrial species owing to fewer barriers to gene flow and increased connectivity resulting from greater dispersal abilities (Cano et al, 2008)
According to population division of E. japonicus based on fishery resources and ecological studies (Hayashi, 1961; Iversen et al, 2005), a total of 389 fish specimens were collected from six main oceanographical regions of the northwestern Pacific including the Bohai Sea population (BHS), the Northern Yellow Sea (NYS), the Northern East China Sea (NES), Taiwan coastal waters (TWC), the Japan Sea population (JPS), and the Pacific side of Japan (JPP)
Summary
Different fish stocks may respond differently to fluctuations of environmental factors as well as fishing pressures. Population Genomics of Engraulis japonicus connected, which might be attributed to large population sizes as well as fewer barriers to gene flow in marine environment (Shanks et al, 2003; Conover et al, 2006; Cano et al, 2008). The adult stage of some marine fish species can be more mobile than the larval stage as they exhibit migratory behavior. Considering all these biological characteristics, it is expected that marine fishes would be highly connected due to high levels of dispersal over large spatial scales, which makes it more challenging to accurately characterize the population structure. Ocean currents can form fronts between distinct water masses, which may act as gene flow barriers as well as selection pressures, and leading to genetic heterogeneity among continuously distributed populations of marine organisms (Saunders et al, 1986)
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