Factors affecting the habitat selection of tench in a shallow eutrophic lake

The activity patterns and habitat selection of tench in a shallow eutrophic lake were determined by radio telemetry. Environmental variables, including prey availability, depth and vegetational composition were quantified in order to explain observed patterns of distribution. Tench were generally only active at night, foraging on benthic animal prey, particularly chironomid larvae. Feeding fish clearly selected for particular locations although only weak associations with depth and densities of preferred prey were found. In addition, it appears that fish spent a considerable time searching for prey and travelling relatively large distances in the process, with the result that only relatively few prey were ingested during the course of a night. During daylight, fish were almost completely inactive, resting together in favoured locations and displaying a strong association for the littoral emergent vascular plant, Typha angustifolia . This may be because Typha usually grows in relatively deep water and forms stands of relatively widely spaced stems, thus allowing such large fish to penetrate deeply into cover. Management of eutrophic waters to encourage tench should take this habitat preference into account.