Weight growth of different generation of the trout Parasalmo mykiss on Lake Imandra

The averaged indicators of the weight growth of four generations of trout at different temperatures in the time interval of the life cycle from the transfer of larvae to cultivation until the fish reaches a portioned commercial weight of 400 g when the first withdrawal of products for sale takes place have been analyzed. It has been shown that fish of different generations passes into the weight category "goods" sequentially, but after reaching different ages, while there is no direct correlation between the terms "generation formation" – "first withdrawal for sale". According to our data the most intensive weight growth of fish has been noted in the temperature range equal to 8–13 °C. An increase in the water temperature in the cages to 15–18 °C has led to a slowdown, and then to the suspension of the accumulation of fish biomass. In cages operating in the area of Kola NPP heated water trout of April generation gains the commercial weight of 400 g in 7–8 months after landing of larvae for cultivation, November trout – after 15 months. Trout of October and January generation reaches commercial weight at 11 and 9 months, respectively. The stretching of timing of biomass accumulation is most pronounced in the autumn generation of trout. It has been found that the greatest increase in weight per unit body (145.1 mg per day) is provided by the trout of the January biological group, the smallest – by the November trout (75.8 mg per day). The energy reserve of heat allowing for differently derived individuals to reach a commodity weight of 400 g, is in the range from 3 320 to 5 300 degree-day.