Characteristics of biology and fishery of roach (Rutilus rutilus L.) in water bodies of the Republic of Karelia

The article summarizes the results of long-term observations of the status of roach stocks in the main fishing waters of the Republic of Karelia (Lake Onega, Lake Ladoga, Vodlozerо and Topo-Pyaozerо reservoirs, Lake Syamozero). New data on its biology (distribution, linear and weight indicators, abundance, biomass) have been presented. There has been shown the dynamics of roach catch for a long-term period (1950–2017). It has been found that the fishing capacity of the represented roach populations corresponds to the production capabilities of its mature part and to the value obtained by biomass growth. The results of observations showed that in the studied water bodies the number and stocks of roach allow for greater volumes of catch than it is currently available and the total catch can be increased up to the calculated values of the allowable catch subject to rational fishing in the water bodies. Roach should be commercially caught at the age of 4+ years old. Given the interspecific contradictions of roach and bream, intensive fishing is recommended during the period of spawning in the straits, bays and mouths of rivers. For catching roach, it is necessary to use coastal-type fishing gear (trap nets, seines). The intensity of fishing and the increase in catches in reservoirs should be considered as mandatory measures in terms of biological reclamation in water bodies. When allocating catch quotas, the priority should be given to the most productive roach suppliers. The accompanying factor for the wide distribution of roach, along with other spring-spawning carp species (blue bream, bream), in our opinion, is warming of the climate in the region. In this regard, it is necessary to take measures to force catching the above fish species.