The Annual Reproductive Cycle of Rudd, Scardinius erythrophthalmus (Cyprinidae) from the Lower Oder River and Lake Dąbie, (NW Poland)

Abstract

The rudd is a common freshwater species of the European ichthyofauna, however, this species' sexual cycle has not yet been described based on the histological analysis of its gonads. The aim of this study was to analyze the annual gonad development cycle of rudd from the watercourses of north-western Poland. Adult individuals aged 2+ to 13+, of both sexes were caught in the Oder River and Lake Dąbie. A standard paraffin technique and six-stage scales were used to assess the development of gonad maturity in both sexes. Rudd gonads developed similarly in the Oder River and Lake Dąbie. Eggs were deposited in batches from the beginning of May to the half of June. Females deposited at least two batches of eggs. In the majority of females collected from these sites, the gonads developed asynchronously throughout the year. Rudd males attained reproductive readiness in the same period as the females, but retained gametes in their gonads for a month longer than the females. Rudd avoid locations with warmer water discharged from power plants.