Evidence of unidirectional gene flow in a fragmented population of Salmo trutta L

publishedVersio

SNP genotyping reveals substructuring in weakly differentiated populations of Atlantic cod (Gadus morhua) from diverse environments in the Baltic Sea

Atlantic cod (Gadus morhua) is one of the most important fish species in northern Europe for several reasons including its predator status in marine ecosystems, its historical role in fisheries, its potential in aquaculture and its strong public profile. However, due to over-exploitation in the North Atlantic and changes in the ecosystem, many cod populations have been reduced in size and genetic diversity. Cod populations in the Baltic Proper, Kattegat and North Sea have been analyzed using a species specific single nucleotide polymorphism (SNP) array. Using a subset of 8,706 SNPs, moderate genetic differences were found between subdivisions in three traditionally delineated cod management stocks: Kattegat, western and eastern Baltic. However, an FST measure of population differentiation based on allele frequencies from 588 outlier loci for 2 population groups, one including 5 western and the other 4 eastern Baltic populations, indicated high genetic differentiation. In this paper, differentiation has been demonstrated not only between, but also within western and eastern Baltic cod stocks for the first time, with salinity appearing to be the most important environmental factor influencing the maintenance of cod population divergence between the western and eastern Baltic Sea

Recent genetic changes in enhanced populations of sea trout (

The genetic structure of a fish population is usually thought to be stable over time. In the southern Baltic, Salmo trutta m. trutta (sea trout) populations have been characterized by low degree of genetic differentiation. All studied populations had been heavily stocked with mixed material for many years prior to the sampling period, including releases of Pomeranian sea trout to the Vistula River in Poland, Southern Baltic. However, the strategy of stocking became river based a few years before the sampling began. Juveniles from artificial reproduction are released only to their parental river, which reduces the mixing of the gene pool of fish from different populations. Changes in sea trout populations in the southern Baltic over time were studied using single nucleotide polymorphisms (SNPs). Genetic composition of populations of sea trout in the Vistula and Drwȩca river system were found to increasingly resemble the non-admixed hatchery population from Aquamar (Miastko, Poland), whereas the Pomeranian populations were stable. The implementation of a new stocking strategy for the restoration and protection of Vistula sea trout was noted as possible explanation. With the increase of natural breeding, artificial enhancement of sea trout populations should be reduced

MOESM1 of The genetic relationship between extirpated and contemporary Atlantic salmon Salmo salar L. lines from the southern Baltic Sea

Additional file 1. Methodology used in this study. This file describes the methods applied in this study [20–29]

Genetic Differentiation in Hatchery and Stocked Populations of Sea Trout in the Southern Baltic: Selection Evidence at SNP Loci

publishedVersio

Genetic Differentiation in Hatchery and Stocked Populations of Sea Trout in the Southern Baltic: Selection Evidence at SNP Loci

publishedVersio

Evidence of unidirectional gene flow in a fragmented population of Salmo trutta L

Selection, genetic drift, and gene flow affect genetic variation within populations and genetic differences among populations. Both drift and selection tend to decrease variation within populations and increase differences among populations, whereas gene flow increases variation within populations but leads to populations being related. In brown trout (Salmo trutta L.), the most important factor in population fragmentation is disrupted river-segment connectivity. The main goal of the study was to use genetic analysis to estimate the level of gene flow among resident and migratory brown trout in potential hybridization areas located downstream of impassable barriers in one river basin in the southern Baltic Sea region. First, spawning redds were counted in the upper river basin downstream of impassable barriers. Next, samples were collected from juveniles in spawning areas located downstream of barriers and from adults downstream and upstream of barriers. Subsequently, genetic analysis was performed using a panel of 13 microsatellite loci and the Salmo trutta 5 K SNP microarray. The genetic differentiation estimated between the resident form sampled upstream of the barriers and the anadromous specimens downstream of the barriers was high and significant. Analysis revealed that gene flow occurred between the two forms in the hybridization zone investigated and that isolated resident specimens shared spawning grounds with sea trout downstream of the barriers. The brown trout population from the river system investigated was slightly, internally diversified in the area accessible to migration. Simultaneously, the isolated part of the population was very different from that in the rest of the basin. The spawning areas of the anadromous form located downstream of the barriers were in a hybridization zone and gene flow was confirmed to be unidirectional. Although they constituted a small percentage, the genotypes typical upstream of the barriers were admixed downstream of them. The lack of genotypes noted upstream of the barriers among adult anadromous individuals might indicate that migrants of upstream origin and hybrids preferred residency