Exterior indicators and physiological signs'' Indices of juveniles Salmo salar L. in the rivers of the Kola peninsula

The range of background values of main parameters of the exterior and indices of morphophysiological features of autumn juvenile salmon Salmon salar L. in four rivers of the Kola Peninsula not affected by hatchery production have been investigated. The importance of such studies is associated with intensification of artificial reproduction of salmon and occurrence of hatchery fish with characters different from wild individuals in the rivers. Currently hatchery reproduction of Atlantic salmon is not carried out in the European North of Russia, however, the need to choose a local salmon population for further hatchery reproduction is obvious. Accumulation of biological data on salmon in the rivers of the Kola Peninsula is important for population monitoring of wild stocks. Samples of juveniles widely varying in size have been collected by electrofishing in the Rivers Pechenga, Zapadnaya Litsa and Titovka of the Barents Sea basin, as well as in the tributaries of the River Varzuga inflowing the White Sea. For each sample individual and group indices of elongation, girth and massiveness have been calculated. The physiological state of the fish has been assessed with allowance for the fatness factor (according to Clark) and indices of internal organs. It has been found that in the autumn season (September) the average statistical values of the morphological indices characterizing the appearance of the fry from four rivers differ with a high degree of reliability. Individual fluctuations in morphological parameters are in the range of values: elongation - from 311 to 725 %; girth - from 41 to 85 %; massiveness - from 150 to 530 %. The mean values of morphophysiological indices for each of the four river populations have been presented. The obtained values of the studied parameters of juveniles of Atlantic salmon can be used for subsequent monitoring of populations.