Frontiers in Marine Science (Dec 2015)
Status and restoration of salmon (Salmo salar L.) stocks in the Nemunas River Basin, Lithuania
Abstract
Dynamics of salmon resources is of a great importance to most countries in the Baltic Sea region, including Lithuania. Currently, human activity is the main cause of negative impact on salmon stocks status mainly through habitat loss. Salmon restocking program started in 1998 with the aim to recover stocks in the Nemunas River basin. The program involved artificial rearing, construction of fish ladders, protection of spawning grounds, stock monitoring, fishery regulation in the sea and rivers. Our study presents data on salmon stocks status and productivity in Lithuania, including abundance of fry and smolts, age composition and genetic structure of the populations. In total, 12 rivers in Lithuania have salmon populations, but the status of the populations varies. Despite the many measures taken, smolt production in Nemunas basin is increasing slowly. Notable increase in production was observed only in recent years. Production increased substantially during 2007- 2010 period, from 13 thousand individuals to over 47 thousand. Salmon parr density in studied rivers varied from 0.3 – 33.7 per 100 m² (mean value 9.8 individuals per 100 m²). Mitochondrial, microsatellite and SNP DNA markers were used to investigate genetic structure of salmon populations. MtDNA was subjected to RFLP analysis, 17 microsatellite loci were used as markers, also samples genotyped with 5568 SNPs. Salmon population from the Nemunas basin was fixed at one haplotype for mtDNA and fell into the same group as the populations from Latvia, Estonia, Russia and Southern Sweden. Microsatellite DNA and SNPs demonstrated distinctiveness from other neighboring populations, however it also indicated lower genetic variability, which could be caused by bottleneck event.
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