© 2006 International Council for the Exploration of the Sea
Annual changes in the proportions of wild and hatchery Atlantic salmon (Salmo salar) caught in the Baltic Sea
Finnish Game and Fisheries Research Institute PO Box 2, FIN-00791 Helsinki, Finland
*Correspondence to M-L. Koljonen: tel: +358 205 751 315; fax: +358 205 751 201. e-mail: marja-liisa.koljonen{at}rktl.fi.
DNA-level information from an eight-loci microsatellite baseline database of 32 Atlantic salmon (Salmo salar) stocks was used with a Bayesian estimation method to assess the stock and stock group proportions of Finnish salmon catches in the Baltic Sea area. The proportions of seven stock groups, important to fisheries management, were assessed in catch samples taken between 2000 and 2005. In the Gulf of Bothnia area, the proportion of wild fish in catches showed an increasing trend in all areas until 2003, mainly because of the decrease in total catches caused by the relatively greater mortality of hatchery-reared fish compared with wild fish. In 2004, the total number of wild fish caught had also increased, indicating an increase in the abundance of wild stocks. In catches from the Åland Sea, the proportion of wild fish increased from 44% in 2000 to 70% in 2004, while the catch during the same period increased from 4628 to 7329 fish. In the Gulf of Finland, the local Neva salmon stock, which is released by Estonia, Finland, and Russia, made the largest contribution. In the western part of the Gulf of Finland, fish originating in the Baltic Main Basin also made a substantial contribution to catches. The threatened eastern Estonian and Russian wild stocks were recorded only in the western part of the Gulf of Finland, where the proportion of wild fish increased from 9% in 2003 to 19% in 2004.
Keywords: Atlantic salmon, DNA, microsatellites, stock mixture analysis
Received 30 September 2005; accepted 7 April 2006.