Frequencies of lateral morphs in different age classes of the flounder Platichthys flesus (Pleuronectidae) from the White Sea

In the populations of the European flounder Platichthys flesus (Linnaeus, 1758), the proportions of left- and right-sided individuals vary widely, and possible causes of this variation remain little explored. The hypothesis of ecological segregation of phenotypical morphs in the European flounder relies primarily on observations of certain differences in morphology and foraging performance between the left- and right-sided individuals. The flounders of different sex and size/age, however, can differ in the character of biotic associations with the environment and other hydrobionts. We have examined the interaction of size/age and sex of the fish with the probability of encountering left-sided individuals in 4 populations of the European flounder from the White Sea basin. The results of the study have shown that the proportion of the reversed individuals did not differ among the flounders of various size and age in all the populations studied. The proportion of the left- and right-sided morphs in different size-age classes in all investigated populations did not depend on the sex of the fish. Revealed interpopulation diversity of phenotypic composition of flounder from the White Sea is not connected with the size/age and sex structure of compared samples.