Sandimirov S.S. Assessment of the habitat conditions for the freshwater pearl mussel Margaritifera margaritifera (l.) In the headwaters of major rivers of Murmansk region. Conservation of freshwater pearl mussel Margaritifera margaritifera populations in Northern Europe. Proceedings of the International Workshop. Karelian Research Centre of RAS. 2010, p. 29-34.

N.A. Kashulin, V. A. Shirokov, S. S. Sandimirov, L. L. Shchurov, P. M. Terent'ev, D. B. Denisov, S. A. Valkova ASSESSMENT OF THE HABITAT CONDITIONS FOR THE FRESHWATER PEARL MUSSEL MARGARITIFERA MARGARITIFERA (L.) electrofishing following the technique by Zippin (1956) and Karlstrem (1976). Each individual was analyzed for weight, length and age (by scales). Mussel surveys. The presence of M. margaritifera in the rivers was estimated by visual examination of the bottom and by findings of shells on the banks. The mussels were analyzed for weight, length and age (Semyonova et al., 1992; Prokhorov, 1995, 1996; Zyuganov et al., 1993, 1998, 2000, 2001). RESULTS Hydrochemistry. The river sites surveyed have the following hydrochemical characteristics: Tsaga River (pH - 5.93-7.26, mineralization -9.8-43.8 mg/l, oxygen content - 8.87 mg/l, oxidation capacity - up to 8.63 mgO/l, water colour - 16-96°); Kitsa River (pH - 6.33-7.21, mineralization - 14.1-54.0 mg/l, oxygen content - 8.03 mg/l, oxidation capacity - up to 12.12 mgO/l, water colour - 30-144o); Pana River (pH - 6.04-7.16, mineralization -5.15-51.1 mg/l, oxygen content - 8.02 mg/l, oxidation capacity - up to 8.12 mgO/l, water colour - 24-5 8o). Analysis of P, N, Fe and organic matter content in the investigated river sites demonstrated a similar pattern during the period of 2004-2008, but the values of these elements in the Kitsa River and the Tsaga River were higher than in the Pana River. P, N and Fe content showed high variation in all the rivers studied (Fig. 2). Fig. 2. Long-term data on some hydrochemical parameters (organic matter, P, Fe and N) in the surveyed river sections Water mosses. Seven moss taxa were found in the investigated river sites: Pana River (Fontinalis antipyretica Hedw., Fontinalis dalecarlica B.S.G.); Tsaga River (Warnstorfiafluitans (Hedw.), Campilium sp.; Ochyrea alpestris (Sw. ex Hedio), Bryum sp. ); Kitsa River (Hygrohynella ochracea (Turn. Ex Wils.)). These mosses are widespread arctic and polar taxa typical of oligotrophic waters. Fish fauna. On the whole, the most common fish species in the headwaters of the rivers are: Thymalllus thymallus (L.), Lota lota (L.), Perca fluviatilis L., Esox lucuis L. and Phoxinus phoxinus (L.). The most favorable conditions for spawning and growth of salmonids were found in the Chernaya River (Pana River tributary) and in the Pana River (at the confluence with the Chernaya River), where S. salar parr were registered (Fig. 3, Tab. 1). Downstream of where the Chernaya River empties, Pana has all the characteristics needed to maintain salmon spawning, as well as salmon parr and the freshwater pearl mussel. 31