EFFECTS OF ACIDIFICATION DUE TO EMISSIONS FROM THE KOLA-PENINSULA ON FISH POPULATIONS IN LAKES NEAR THE RUSSIAN BORDER IN NORTHERN NORWAY

In this paper we document the effects of acidification on fish populat ions in lakes in Sor-Varanger near the Russian border in northern Norw ay. We used questionnaires in order to assess the current status and d istribution of different fish species, and conducted test-fishing to d etermine relative abundance (CPUE-T) and age structure. Acidification of surface waters in this area is due to emissions of SO2 from smelter s on the Kola Peninsula in Russia (Nikel and Zapoljarnij) between 10 a nd 30 km from the Norwegian border. Sulphur deposition in Sor-Varanger ranges from 0.6 to 2.0 g S m(-2) yr(-1), which is similar to levels i n the most acidified areas in southern Norway. However, a dominant fra ction of the acidic deposition reaches the ground in particulate form during summer and autumn. Coastal areas in Sor-Varanger receive small amounts of precipitation; the annual mean is 580 mm. We obtained fish status from 401 lakes, about 40% of all lakes larger than 3 ha, which were inhabited by 236 and 293 populations of Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta), respectively. The extent of f ish damage was small as only three populations of Arctic charr were lo st, while three populations of Arctic charr and eight populations of b rown trout were at various stages of reduction. Damaged and lost fish populations were identified in smaller lakes at relatively high elevat ions (172-349 m) in six areas in the Jarfjord Mountains, covering a la nd area of 30.0 km(2). Most of the damage probably occurred during the 1970s and 1980s. In lakes that supported or had supported Arctic char r and brown trout, we found a significant relationship between CPUE-T, and acid neutralizing capacity (ANC) and pH, and also between alkalin ity and the concentration of inorganic Al for brown trout. In both spe cies, the catch of fish in age groups 1+ and 2+ (CPUE-R) increased sig nificantly with CPUE-T. Affected populations typically exhibited irreg ular age composition, and age-classes were missing, indicating that re ductions in fish populations were due to recruitment failure. The limi ted fish damage is related to relatively good catchment resistance to acidic inputs, small amounts of wet deposition as well as precipitatio n. These conditions result in low accumulation of acidic compounds, pr oducing less acidic run-off waters and few episodes of unfavourable wa ter quality.