Life cycle of Gammarus pulex (L.) in the River Yeşilirmak

Abstract

Monthly sampling of Gammarus pulex for 45 months in the River Yeşilirmak showed that the mean seasonal population density increased to a maximum in summer, and then declined to the lowest level in winter. There was a consistent seasonal pattern of body length distributions, characterised by the arrival of a strong cohort of new juveniles in spring and early summer. The ovigerous adults were few in autumn, peaked around January to March, and were virtually absent from July to October. Estimated sex ratios obtained from the field in general seem to show that females predominated, except in summer. © TÜBİTAK.