Movement pattern and growth ratio tagged fish in two lowland rivers of Central Poland

Using a mark-recapture technique in two lowland rivers, movements of ten fish species were investigated. Both rivers, the Pilica (the Vistula River system) and Warta (the Odra/Oder River system), located in Central Poland, are lowland, alluvial, meandering but dammed in the middle course. Reaches selected for the study have an almost natural structure (bottom structure, banks, vegetation). The subject of the study were cyprinids (barbel Barbus barbus (L.), chub Leuciscus cephalus (L.), dace Leuciscus leuciscus (L.), ide Leuciscus idus (L.), roach Rutilus rutilus (L.), bream Abramis brama (L.), tench Tinca tinca (L.) and giebel Carassius auratus gibelio (Bloch), as well as pike Esox lucius L. and perch Perca fluviatilis L. (predators) which in summer and autumn have realized life history strategies in small home section lengths (HSL), although undertaking ‘round-trip movements’. For a few species in the study the HSL values were equal or smaller than the calculated median displacement distances (MD). The neighboring man-made reservoirs have affected some individuals which moved dozens km from a channel to the reservoir. Body weight increase recorded for more abundant species at investigated rivers (pike and chub), shows that an individual can keep the same body weight for a long time or grow faster than it was described before.