Age and growth of European flounder from the Chupa Inlet (Kandalaksha Bay, the White Sea)

Abstract

We studied age structure, growth and distribution of European flounder Platichthys flesus at the sea in Chupa Inlet (Kandalaksha Bay, the White Sea). Immature and mature fishes fed at shallows of Chupa Inlet and adjacent open sea area in June-August. Size-age and sex composition of fishes in catches are presented in the paper. Individuals of 17–27 cm length and 4–5 year age constituted the majority of catches (45%). On the whole, males numerically predominated over females in the samples. Analysis of sexual differences of growth has shown that females grew faster than males. The most intensive growth took place in July–August, according to the increments on the otoliths. Growth rate of the flounder from Chupa Inlet appeared to be similar to the growth rate of the flounder from other open shore sites of Kandalaksha Bay. We have compared also peculiarities of growth and age structure of flounder populations from Kandalaksha Bay to those from other bays of the White Sea. Significant differences of the growth rate were found between flounders from Kandalaksha, Onega, Dvina and Mezen' Bays. Both males and females from Onega Bay grew faster than other. Growth rate of fish decreased towards the north (Kandalaksha Bay) and the north-east (Mezen' Bay). The most slow-growing flounder inhabited shallows of Mezen' Bay. Statistical analysis has shown that age structure of flounder populations varied in different bays of the White Sea, and observed regional variations were characteristic for both males and females. Flounder population in Onega Bay was characterized by the dominance of the younger individuals compared to populations in other bays. The greatest mean age of flounder was registered in populations from the north-west (Kandalaksha Bay) and the north-east (Mezen' Bay) parts of the White Sea. Males and females in populations from Onega and Dvina Bays differed significantly in the mean age, and as a rule females were older. No age differences between sexes were found in flounder population of Mezen' Bay. We suppose that temperature conditions were among the main factors influencing regional differences in growth rate and age structure of the flounder populations in the White Sea.