Biological characteristics of European whitefish in Lake Pulmankijarvi, northern Finland

Lake Pulmankijarvi is a subarctic oligotrophic lake that forms part of the Teno River system on the Norwegian-Finnish border. European whitefish (Coregonus lavaretus (L.)) accounted for over 80% of fish caught. Two forms of European whitefish were identified: a sparsely-rakered form with 2030 gillrakers and a medium-rakered form with 35-46 gillrakers. Of the European whitefish, the sparsely-rakered variety formed the bulk of catches (93%). Over-abundance, poor food supply, and the possible effect of toxicants are thought to have affected the age structure and reproductive condition of the populations.