Characteristics and movement patterns of a recently established invasive Pacifastacus leniusculus population in the river Mura, Croatia

The presence of the signal crayfish, Pacifastacus Ieniusculus, in waterbodies of Europe is of high concern due to its potentially major ecological impact on invaded ecosystems and native crayfish. In this study, we examined population characteristics and spatial dynamics of a recently established signal crayfish population near the edge of its invasive range in the Mura river (Croatia), by analyzing population density, fecundity, and sex and size structure, as well as movement patterns. The obtained results revealed that the examined population is characterized by relatively low population density, balanced sex and size structure of adult crayfish, and high spatial activity of examined individuals, with an average daily movement of 28 m/day. Pleopodal fecundity was in a similar range to other signal crayfish populations in Europe. The large minimal size of caught mature females (85 mm total length), coupled with the estimated low population density (0.8-1.2 crayfish.m(-2)), suggested that the examined population has not reached its maximum density yet. Obtained results represent baseline information for the development of monitoring procedures and management strategies aimed at signal crayfish control within the Mura and Drava catchments and also highlight the importance of understanding local factors controlling invasive species' population dynamics and productivity.