Sjølaksefiske i Finnmark: Ressurs og potensial Del II - Genetisk opphav hos atlantisk laks (Salmo salar) fanga av sjølaksefiskere langs kysten av Finnmark sommeren og høsten 2008
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- Fisken og havet (1958- ) 
A multistock Atlantic salmon (Salmo salar) sea-fishery operates off the coast of Finnmark, the northernmost county in Norway, where the average annual landings the last 15-20 years have been 200-300 tonnes. This is approximately equal to the total annual river landings in the 43 Finnmark rivers. The total river and sea-fishery catch in Finnmark constitutes around 50 % of the total catch of Atlantic salmon in Norway. The salmon sea-fishery in Finnmark has long cultural traditions, and has been under strong debate the last 10 years, due to the complexities involved in the potential mixed stocks harvesting, especially since Russian salmon from more than 60 Kola rivers may also 7 be harvested during their homeward spawning migration. To increase our knowledge of adult Atlantic salmon along the Finnmark coastal area, the Kolarcticproject ”Sea salmon fishery – resources and potential” was initiated in summer 2008. The project was a co-operation between Norwegian Institute for Nature Research (NINA-Tromsø), Finnish Game and Fisheries Research Institute (RKTL), The County Governor of Finnmark and the three sea-fishery organizations in Finnmark. From 2009, the Institute of Marine Research (IMR-Bergen) and the Polar Research Institute of Marine Fisheries and Oceanography (PINRO-Murmansk) were included and from 2010 also the University of Turku. Between mid May and late July 2008, more than 4 200 salmon were captured (hook net and keyway) by local sea-fishermen along the Finnmark coast. All fish were measured and weighed, their sex and maturity defined, the number of sea lice counted, and their stomachs frozen. Scales were sampled from all fish, and 3 000 individuals were analyzed for microsatellite genetic markers, in an attempt to define country, region and/or specific river origin of each salmon. To determine the origin of the salmon caught in the sea fisheries, the genetic data of individuals were compared to a database of genetic profiles from 51 rivers in north Norway and Russia, using statistical assignment methods. These methods assigned each fish with a given probability to possible source populations. The precision of the assignment depends both on the coverage of the genetic baseline and the number and variability of the genetic markers used. In this study, we compared the performance of two different baselines; one consisting of 18 microsatellite markers covering all rivers, but with a limited coverage of the River Tana, the largest river within the survey area, and one consisting of 12 microsatellite markers with a more complete coverage of the Tana River system. The results showed that while the precision in general (measured as correct assignment to home river) achieved was higher using the 18 marker baseline, the limited coverage of the Tana system led to mis-assignment of fish belonging to this river system to other rivers in the region. There was, however, a general tendency for mis-assigned fish to be assigned to rivers within the same region, consistent with an isolation by distance pattern, where geographically close populations are more similar than distant ones. In Western Finnmark, the proportion of 1- and 2-seawinter Russian salmon in the catches decreased from 60 % in May to ca 10 % in July (given a precision level of p>0.7), suggesting that Russian salmon approached the Finnmark coast from the west in summer 2008. The proportion of 3- seawinter Russian salmon was, however, very low (< 3 %) during the entire fishing season (May- July). The proportion of Tana salmon in western Finnmark decreased from 18 % in May to 12 % in July, whereas all Tana salmon captured in western Finnmark in May were 3-seawinter salmon. The amount of 1-seawinter (small) Finnmark salmon increased during summer, indicating that also small Finnmark salmon approached the coast from the west, although significantly later than the larger salmon (2- and 3-SW). In Eastern-Finnmark (Varanger fjord) the proportion of Russian salmon was fairly high during the entire fishing season, although deceasing from 67 % in May to 50 % in late July. Also the amount of large Russian salmon (3- and 4-seawinter) was very high in May (70 %), but decreased significantly during summer, being less than 15 % in late July. The relatively high incidence of large Russian salmon in Eastern Finnmark in May may indicate that the larger salmon have a different migration patterns, and/or use other feeding areas, compared to salmon from the Norwegian/Finnmark rivers. The incidence of Russian salmon was low in the catches within the Tana fjord, while the amount of Tana salmon in the catches was at the same level both from western and eastern Finnmark. This may indicate that Tana/Finnmark salmon, after feeding in winter in the Barents Sea, may approach the Finnmark coast both from west, north and east. Some salmon/populations may, however, feed in the eastern coastal area in winter. The migration patterns of Atlantic salmon along the Finnmark coast in summer may thus be very complex. Our results illustrate that by developing a genetic base line for Atlantic salmon populations in North-Norway and Russia, it is possible to document the genetic origin of salmon caught along the 8 Finnmark coast. By expanding the number of baseline rivers and increasing the number of genetic markers, we will be able to not only confirm from which home region or country the salmon originate, but also determine the home river for each salmon caught. In 2013, during the new Kolarctic-salmon project (2011-2013), an improved baseline will be finalized, giving the management authorities a new tool to ensure a future viable exploitation of the northernmost Atlantic salmon populations in Europe.