%0 Generic
%A Papa, Laura
%D 2009
%F heidok:9840
%K Atlantischen Lachs, Salmo salar, Population genetische, Allozym-Analyse, Mikrosatelliten, Schuppen AnalyseAtlantic salmon, Salmo salar, genetic population, Allozyme analysis, Microsatellite, Scales analysis
%R 10.11588/heidok.00009840
%T Genetic Analysis of a Population of Atlantic salmon (Salmo salar, L.)in the Rhine System
%U https://archiv.ub.uni-heidelberg.de/volltextserver/9840/
%X The present study was developed under the guidelines of a regional project to support the management of the anadromous salmonids in the Rhine, particularly the reintroduction of the Atlantic salmon (Salmo salar, L.) The main aim was to assign the salmons ascending to the Iffezheim lock to salmons used for reintroduction in the Rhine. It was analysed if such an assignment was reasonably possible. Furthermore, we wanted to find out if an established Rhine population already exists. The Ph.D. study started in April 2005 and was supported by voluntary field workers who sampled and checked the fish ladder at Iffezheim (Landesfischereiverband Baden). Genotypes, based on the analysis of polymorphic microsatellite loci, of the sampled year-classes from 2002 to 2005 inclusive, have been analyzed, and referenced to suitable outgroup populations. An overall amount of 180 salmon samples have been analyzed (65 from Rhine/Germany, 22 from Burrishoole/Ireland, 50 from Allier/France, 28 from Ätran/Sweden and 15 from Lagan/Sweden). An allozyme analysis was performed in order to identify individuals which eventually were misidentified during the sampling with brown trout or hybrids from the two species. 11 fishes out of the 304 analyzed turned out to be misidentified trouts given as salmons. Microsatellites genotyping involved sixteen primers, two STR (Short Tandem Repeat) amplified for two loci, and nine loci (SSOSL85, SSOSL311, STR15, Ssa171, Ssa402*, Ssa402**, Ssa408, Ssa202 and Ssa411).  Genetic similarities have been evaluated by means of population genetics and forensic assignment statistics of individuals.  Analysed individuals were all in HWE (Hardy-Weinberg Equilibrium). Heterozygosity ranged from 0.60 to 0.79. Analysis of allele frequencies revealed a heterozygotes deficiency and a significant genetic drift. A Whalund effect was supposed to lie behind this homozygote excess. By the bottleneck analysis no evidence of recent reduction in population size has been observed in the Rhine subpopulation according to TPM (two-phase model) and SMM (stepwise mutation model). The assignment tests showed that the Rhine subpopulation shares only a small fraction of alleles with the hatchery populations. Swedish genotypes seemed to be the most representative. Swedish individuals showed the best adaptation and reproductive success with high rates of returning individuals. Total of 118 private alleles have been found, the majority of them with a frequency equal or below 0.06. A high rate of private alleles have been found among the Rhine individuals that could be used as genetic markers in order to identify individuals of this cohort and eventually select them for a proper stocking program. The genetic differentiation analysis showed that the Rhine subpopulations cluster together with a significant distance among the other subpopulations (Fst ranged from 0.079 of BUR to 0.051 of Allwild and Lagan and from 0.035 to 0.012 within Rhine subpopulations). According to the results obtained by the neighbour-joining and the UPGMA analysis, both based on genetic distance, 4 main groups were clearly defined: 1.Rhine individuals, divided per sampled year (from 2002 to 2005); 2.Swedish individuals from hatcheries (Ätran/Lagan); 3.French individuals from hatcheries (Allhatc/Allwild); 4.Irish individuals from hatcheries (BUR). Rhine individuals clustered together with a significant bootstrap value. Swedish and French individuals clustered together following, as expected, their geographical origins. Irish individuals were considered as the outgroup. Swedish individuals showed the highest degree of genetic similarity to the ones of the Rhine, French and Irish individuals showed the lowest. According to an analysis of scale patterns, Rhine individuals apparently migrate to the sea after at least two years spent in the freshwater and come back to the spawning place after one or two years (called 1 or 2 winters returning, respectively). A few individuals coming back after more than two years (called multi winter returning) have been observed, but rarely. Some useful conclusion can be derived from the results of this study: i) a local adapted Rhine subpopulation should be considered in further projects, ii) stocking and reintroduction of individuals of this local subpopulation, besides the already existing programs, is desirable. iii) Swedish individuals (Lagan/Ätran) should be preferred for stocking programs instead of French and Irish individuals. iv) Conservation programs as “Lachs 2020” are fundamental in order to maintain the Rhine Atlantic salmon populations and to continue with the habitat restoration in order to create more suitable spawning places.