Jarmo Koskiniemi

Maintenance of genetic diversity of Atlantic salmon (Salmo salar) by captive breeding programmes and the geographic distribution of microsatellite variation

Abstract The capability of Finnish Atlantic salmon ( Salmo salar L.) broodstock breeding programmes to maintain genetic diversity was assessed by comparing the levels of microsatellite diversity in wild and hatchery stocks in general, and in wild and hatchery derivatives of the same stock. The effective population sizes ( N e ) of the broodstocks and the ratio of effective size to census size ( N e / N c ) as well as the rate of loss of diversity in captive breeding were assessed. Moreover, the distribution and pattern of genetic diversity among Atlantic salmon stocks in the Baltic Sea, Barents Sea and NW Atlantic were measured. Microsatellite data were also compared with allozyme data of the same salmon stocks. Nine microsatellite loci were amplified: Ssa85, Ssa171, Ssa197, Ssa202, Ssa289, SSOSL85, SSOSL 311, SSOSL417 and SSOSL438 from 11 Atlantic salmon stocks. The effective population sizes of broodstocks were estimated with the method based on temporal allele frequency change. In short-term breeding programmes, the average rate of loss of heterozygosity was 1.4% per generation and the average observed rate of loss of alleles was 4.7% per generation. The estimated N e s for the broodstocks were 32 and 238. The average N e / N c ratio was 0.81. Changes in present-day broodstocks were not alarming and the N e / N c ratios were higher than in wild populations in general. The genetic D A distance between continents was 0.64 ( F ST ( θ )=0.22) and distances about half of that level ( D A distance 0.34, F ST =0.09) were measured between European and Baltic Sea salmon stocks. A nearly diagnostic difference was observed in the SSOSL311 of the North American stocks (Maine 0.982 and Labrador 0.957) for a single allele (SSOSL311 118 ) that did not occur in European populations at all. Microsatellite data showed relatively more genetic differentiation ( F ST =0.040) on a small geographical scale than did allozyme data ( F ST =0.017), indicating the higher discrimination power of this data set.

Wild Estonian and Russian sea trout (Salmo trutta) in Finnish coastal sea trout catches: results of genetic mixed-stock analysis

For responsible fisheries management of threatened species, it is essential to know the composition of catches and the extent to which fisheries exploit weak wild populations. The threatened Estonian, Finnish and Russian sea trout populations in the Gulf of Finland are targets of mixed-stock fisheries. The fish may originate from rivers with varying production capacities, from different countries, and they may also have either a wild or hatchery origin. In order to resolve the composition of Finnish coastal sea trout catches, we created a standardized baseline dataset of 15 DNA microsatellite loci for 59 sea trout populations around the Gulf of Finland and tested its resolution for mixed-stock analysis of 1372 captured fish. The baseline dataset provided sufficient resolution for reliable mixture analysis at regional group level, and also for most of the individual rivers stocks. The majority (76-80%) of the total catch originated from Finnish sea trout populations, 6-9% came from Russian and 12-15% from Estonian populations. Nearly all Finnish trout in the catch were of hatchery origin, while the Russian and Estonian trout were mostly of wild origin. The proportion of fish in the Finnish catches that originated from rivers with natural production was at least one fifth (22%, 19-23%). Two different spotting patterns were observed among the captured trout, with a small and sparsely spotted form being markedly more common among individuals of Russian (28%) and Estonian origin (22%) than among fish assigned to a Finnish origin (0.7%).