Microhabitat preferences and movements of the weatherfish, Misgurnus fossilis, in a drainage channel

Habitat preferences and movements of the weatherfish, Misgurnus fossilis, w ere studied in a drainage channel of the lower River Havel region (Saxony-A nhalt) from July to November 1995. During summer, adult fish preferred dens e vegetation patches (e.g. Elodea canadensis) whereas juveniles preferred t he reed zones along the bank lines, characterized by coarse detritus and ex tremely shallow water depths (< 0.1 m). All size groups totally avoided ope n substratum without vegetation structures. In total, 166 weatherfish great er than or equal to 14 cm were marked individually by injected dyes and the ir movements were documented by recaptures (recapture rate 29%). Most of th e weatherfish showed stationary behaviour or site constancy. The majority o f fish (70.1%) were recaptured within ranges of 50 m with reference to the first release point. The mean movement distances slightly increased during the search for overwintering habitats in the first weeks of October. Weathe rfish stocks in drainage channels of the study area are strongly affected b y annual machine weeding due to depletion of suitable microhabitats and dir ect removal of fish. Alternative maintenance protocols for drainage channel s and ditches are proposed.