Movement patterns of the co-occurring species Astacus astacus (noble crayfish) and Austropotamobius torrentium (stone crayfish)

Crayfish are the largest and most mobile invertebrate animals in streams, and their movement potential is quite high. Thus, detailed knowledge about their movement patterns can influence conservation management and thus the number of crayfish plague outbreaks. The movement patterns of two crayfish species, Austropotamobius torrentium (Schrank 1803) and Astacus astacus (Linnaeus 1758), were investigated in streams of Central Bohemia in the Czech Republic where these two crayfish species co-occur. The observed sections of the streams were divided into segments along which the movement of crayfish was observed. On 11 separate sampling occasions, crayfish were captured by hand and individually marked using a visible implanted elastomer. From 2008 to 2010, a total of 1,079 specimens of A. torrentium and 402 specimens of A. astacus were marked. One hundred and twenty-nine specimens of A. torrentium and 26 specimens of A. astacus were later recaptured. Astacus astacus exhibited a significantly greater tendency to move upstream than A. torrentium. We found no relationship between the length of a crayfish's body and the distance and direction of its movement. We also did not find any significant difference between the movement directions of males and females in either crayfish species. The longest distances recorded for crayfish movement were 133 m downstream in 55 days (female of A. torrentium) and 151 m upstream in 36 days (female of A. astacus). Due to the significantly greater tendency of upstream movement of A. astacus (compared to A. torrentium), we can assume A. astacus to have a generally higher colonising and moving ability than A. torrentium, which tends to be sedentary. The protection of existing localities of A. torrentium appears to be crucial for the conservation and management of the species based on its sedentary behaviour in the stream.