VOLGA UNDERMOUTH <I>CHONDROSTOMA VARIABILE </I>JAKOWLEW, 1870 IN SPAWNING CONGESTIONS OF FISHES IN MIDDLE STREAM OF OKA RIVER IN RYAZAN PROVINCE (RESULTS OF MONITORING IN 1970–2012)
Data of monitoring of Volga undermouth spawning congestions in the middle stream of Oka River are presented in the article. The basic population indicators (growth, age, fertility, morphometric characters of breeders) are presented. Dynamics of relative number of undermouth and its shares in catches is shown, its reasons are analyzed. The work purpose: to carry out a current state of the population indicators of undermouth spawning congestions in the middle stream of Oka River and to analyze factors defining it.