Reproductive traits of the spirlin Alburnoides bipunctatus in the Vistula River basin

The aim of the current study was to examine whether environmental conditions may explain interpopulation variation in fecundity and egg size of the spirlin from two rivers of the Vistula River basin. The obtained results indicated that the reproductive performance, including the gonadosomatic index, was similar in both rivers and fecundity increased with total length of females. The observed differences in water temperatures and flow speed between the rivers were too small to cause discernible differences in the reproductive performance of fish.