Microhabitats and diel downstream migration of young grayling (Thymallus thymallm L.)

SUMMARY. 1, Microhabitats chosen by young grayling ( Thymallus thymallus L.) were investigated by electrofishing. The first feeding habitat was marginal areas where water velocity did not exceed 15 cms −1 . Fry fed on drift in the first 10 cm of the water column below the surface. This location was very stable during the first weeks of growth (mid‐April to mid‐May). When they were 3–3.5 cm long, fry began using benthic areas and gradually moved away from the banks towards the channel. 2. A downstream migration was noted from the beginning of emergence (mid‐April) to the end of May. This mainly nocturnal movement involved all fish sizes and caused a complete removal of young‐of‐the‐year by June from the spawning tributary.