Changes in body shape of male and female perch and roach in sympatric populations of the Verkhne-Vyisky reservoir at various phases of the seasonal cycle

On the basis of multivariate methods of geomet-ric morphometrics in 21 homologous landmarks the author studied changes in the body shape of males and females of the perch Percafluviatilis (Linnaeus, 1758) and roach Rutilusrutilus (Linnaeus, 1758) populations coexisting together in the Verkhne-Vyisky reservoir (the Middle Urals) during breeding and feeding. It was found out that with age and growth the perch and roach had common regulari-ties in the changes of the body shape and its indi-vidual structures. Periodic changes in the body shape of the perch and roach associated with changes in the gonad size at the various phases of the seasonal cycle (breeding and feeding) were 1.2 times less than variability caused by sex and 4.0 times less than variability caused by age and growth. The different morphogenetic reactions were observed in males and females of the perch and roach from sympatric populations living in the same ecological conditions of the Verkhne-Vyisky reser-voir most likely connected with specific biological and ecological peculiarities of the fishes belonging to different taxonomic orders. It was found out that the range of sex differences in body shape was larger in the perch than in the roach. The coordi-nated unidirectional seasonal changes in the body shape in both sexes of the perch and roach was accompanied by increased morphological differ-ences between males and females.The transfor-mation of the body shape between the feeding and spawning periods increased sex differences in the body shape in the perch; while in the roach it creat-ed sex differences in the body shape. During the feeding period the differences between individuals of different sexes were smaller and were observed only in the perch.