Abstract

Activity of Austropotamobius torrentium was investigated for three years (1990 - 1993) by closing a small river in the downstream direction with a fish trap. Every crayfish and fish moving downstream was caught and recorded daily. Crayfish were measured and sexed. Water temperature were also measured daily. A. torrentium begins its activity in early spring (February). Its movement had two peaks: the first one in March/April and the second in June/July. From September until January, however, almost no movement was recorded. Crayfish of 5 to 8 cm total length (TL) were the most active (max. length of this species around 11 cm TL). Activity of A. torrentium in early spring apparently depends both on water temperature and starvation after the winter. Our expectation that the late moulting of females after hatching and releasing the juveniles might be the reason for the activity peak in June/July could not be verified. The activity seems to be a general movement related to the higher water temperature (14-19°C). During the mating -season in October/November, no movement was recorded.

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