Abstract
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.
Highlights
In the southern Baltic, Salmo trutta m. trutta populations have been characterized by low degree of genetic differentiation
Studies, based on microsatellite DNA, in some cases resulted in the observation of temporal changes in the genetic composition, which may be explained by drift in small persisting populations of brown trout (Ostergaard et al 2003)
Salmo trutta m. trutta populations in the southern Baltic have been characterized by low degree of genetic differentiation mainly due to admixture prior to the 1990s
Summary
A range of new molecular genetic techniques have been used to study fish and shellfish evolution, and changes in wild populations including those associated with exploitation, stocking and research related to aquaculture Microsatellites are regularly used in fisheries related applications and research Glover et al (2010) demonstrated that identification of highly informative SNP markers from the screening of larger pools represents a powerful technique to create molecular tools, both to study individual membership of populations and for population differentiation SNPs are biallelic markers characterized by codominant inheritance, lack of homoplasy and an infinite model of mutation (Morin et al 2004; Beacham et al 2010; Seeb et al 2011) Analyzing the drawbacks of use SNPs the most important are lower discrimination power in comparison with microsatellites, non-neutrality, possibility of random genetic drift and ascertainment bias. Glover et al (2010) demonstrated that identification of highly informative SNP markers from the screening of larger pools represents a powerful technique to create molecular tools, both to study individual membership of populations and for population differentiation
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