Seasonal movements and habitat use of river whitefish (Coregonus lavaretus) in the Koitajoki River (Finland), as determined by Carlin tagging and acoustic telemetry

Abstract

In the Koitajoki River, Eastern Finland, there exists a self-sustaining population of river-spawning densely rakered whitefish (Coregonus lavaretus pallasi). The population has been classified as near-threatened due to overexploitation and possible hybridization with the lake-spawning sparsely rakered whitefish form. Thus, knowledge of habitat use, movements, and migrations is important for threat assessment and management decisions. We employed conventional tagging and acoustic telemetry to provide information on movements and home range of the Koitajoki River whitefish. We tagged mature individuals at their spawning areas and followed fish movements by tag recoveries and continuously recording fixed receiving stations. The maximum movement distances were 40–50 km both upstream and downstream from the releasing site. There were indications of a clear seasonal migration pattern and spawning-site fidelity; riverine habitats were mainly occupied for spawning and overwintering, while feeding and growth mainly took place in lacustrine environments within several lakes of the river system. Due to their migratory nature, whitefish is vulnerable to environmental disturbances and overfishing in a large geographic area.