Population characteristics and life cycle of the Lake Baikal invader Gmelinoides fasciatus (Stebbing, 1899) (Crustacea: Amphipoda in Lake Ladoga

Abstract

Dynamics of the size-age structure and sexual structure of the population and characteristics of reproduction and life cycle have been studied in the Baikal invader Gmelinoiudes fasciatus (Stebbing, 1899) in Lake Ladoga. The studied characteristics display both similar features with and differences from populations of this species in other waterbodies. It is found that the size and age structure of the G. fasciatus population changes in the circannian aspect under the influence of complex of environmental factors. The sexual structure of the population is dynamic, but a sex ratio of approximately 1: 1 is maintained in the circannian cycle. Six principal periods of hatching are recognized. The main factor determining the timing of the start and termination of the reproduction period in G. fasciatus is temperature. The weight of eggs oviposited by the female over the whole life cycle (about 21.5 cal in the energy equivalent) amounts to about 60% of the female body weight.