BIOMETRY AND DEMOGRAPHY OF THE INVASIVE CRAYFISH ORCONECTES LIMOSUS IN THE CZECH REPUBLIC

Biometry, population data and selected ecological parameters of populations of the spiny-cheek crayfish, Orconectes limosus, were measured to evaluate the differences between “marginal” (short-time, situated on margins of an area) and “residential” (longterm, well established inside an area) populations of this invasive crayfish. We selected three types of localities: 1. Large rivers – residential (Labe, Vltava); 2. Brooks (small and shallow running waters) – marginal; 3. Isolated standing waters – residential (old sandpits or flooded quarries). No significant differences in the total body length of crayfish were found between running and standing water localities as a whole, or between marginal and residential populations from running waters. There was, however, a low but distinct difference in the body weight between crayfish from brooks and other waters. Larger specimens (up to 116.5 mm in body length) were found only in isolated standing waters, whereas no crayfish longer than 100 mm were found in the rivers. The sex ratio of the crayfish was almost equal in rivers and isolated waters; males were more numerous in brooks. There was a significant difference between male and female body weight-length relations.