Behavioral differences of various ecological groups of roach Rutilus rutilus and perch Perca fluviatilis

The intrapopulation morphological and behavioral polymorphism of roach ( Rutilus rutilus ) and perch Perca fluviatilis ) was studied. It was shown that marker indices for distinguishing intrapopulation groups are the size of the mouth opening and the index of the body shape in roach and the coefficient of pigmentation in perch. Based on analysis of the data of indices, it was found that there are two ecological groups—coastal and pelagic in populations of roach and perch. Several behavioral differences in individuals of various ecological groups were revealed. Comparison of the defense reaction of perch individuals belonging to various ecological groups was performed. The assessment of the effects of hydrodynamic activity on the survival of perch individuals belonging to various ecological groups was made. Differences in the swimming capacity of juvenile roach developing under conditions of biotopes of various types were established. Suggestions were made on the mechanisms of formation of intrapopulation groups of roach and river perch.