Modern biological state of the mass species of the fish of lake Konchezero (Karelia)

The results of a study of the biology of mass species of fish (bream, roach, perch, bleak) of lake Konchezero is presented in this article. The research objective - assessment of the current biological state of mass species of fish of lake Konchezero, a cold water reservoir which is located in the southern part of the Republic of Karelia and falls into to the pool of the lower watercourse of Shuya. Catching of fishes was carried out in the summer (June, July) 2001-2002 and 2017; it is investigated 271 copies of fishes. It is revealed that the basis (56-57 %) in the catches on the lake are perch and roach. Much less (10-11%), but stable number in catches of a bream who remains to one of the most significant fishes of lake Konchezero. The bleak in catches meets in slight quantities (no more than 2%). It is established that in the period from the middle-the end of the last century (the 1950-1990th years) till now there have been changes of age and dimensional and weight structures of the investigated types of fishes in catches on the Konchezero lake towards decrease. It is revealed that body height of small fry in the lake Konchezero rather sluggish. It is noticed that reduction of an age number of a bream, small fry and a perch is bound to disappearance from catches of fishes of advanced age. So, last century in catches the maximal age of small fry was 13+-15+ years, and now in catches the small fry is presented by individuals of an age from 1+ to 7+ years. Natural removal of modal age groups at these species of fish towards younger age is noted. This is the result of a long-term negative impact of a complex of anthropogenic factors (fishery, pollution, etc.) on the fish population and its consequences (eutrophication, changes in the feed base of fish, etc.). Currently, by reducing the pollution intensity of the processes of eutrophication of the reservoir, anthropogenic load on the mass fish species of lake Konchezero it is possible to expect improvement of their populations. The received results are important as for the scientific and educational purposes, and can promote the solution of questions of rational development of fishery branch of the Republic of Karelia.