Dispersal and survival of stocked cyprinids in a small English river: comparison with wild fishes using a multi-method approach

Mark–recapture and fixed-station passive integrated transponder (PIT) telemetry were used to compare movements, distribution and survival of stocked juvenile chub Leuciscus cephalus and roach Rutilus rutilus with those of wild conspecifics. Daily activity of wild fish activity was affected by a combination of river flow and temperature, whereas stocked fishes were not influenced by environmental factors. PIT telemetry recorded exploratory movements of stocked L. cephalus immediately after stocking, a substantial number of stocked fish moved both downstream and upstream during periods of elevated flow, and proportionally more stocked fish moved during the first 6 weeks after release than later on. Proportionally more stocked fish than wild fish moved through PIT antennae, stocked L. cephalus moved greater distances than wild L. cephalus and were more widely distributed than wild fish. Minimum estimates of survival after 5 months were 50·5% for stocked R. rutilus and 28·0% for stocked L. cephalus . Ultimately, stocked cyprinids appeared to be able to cope with elevated flows and most remained in the river section local to the stocking location.