Daily rhythms of food and rations of fish living in the Belaya Kedva River (the Pechora River basin)

摘要

For the basin of the Pechora River the daily rhythm of food and daily diets of juveniles of salmon and European grayling in the period preceding intensive climate changes – in the 70th of the last century – have been presented. Researches were conducted on the River Belaya Kedva. This river is situated in the Komi Republic, proceeds on the eastern part of the Timan Mountains, and falls into the Izhma River which is an inflow of the Pechora River. The range of food of the studied fish living in the River White Kedva is represented mainly by benthic organisms – larvae of amphibiotic insects. As a part of food lumps of juveniles of Atlantic salmon and European grayling 12 groups of invertebrates, juveniles and fish eggs, seaweed and the remains of the highest water vegetation were marked out. Frequency of occurrence of food components in food lumps was different for different types of fishes and different age classes and groups of European grayling. The general for all species of fish and age classes food component met in all digestive tracts was larvae of mayfly. The highest feeding was noted at grayling fingerlings. At salmon juveniles the average index of digestive tracts' filling was lower in comparison with the grayling one. The food relations of grayling and salmon juveniles in the River Belaya Kedva had no expressed competitive character: the maximum index of their food similarity did not exceed 68.5 %. The lack of the notable food competition between juveniles of salmon and grayling is demonstrated also by discrepancy in a daily rhythm of fish feeding.