| Popis: |
The recent finding of the signal crayfish, Pacifastacus leniusculus (Dana, 1852) in the Brugneto Lake (Trebbia River basin, Liguria, NW Italy) raises new management problems. In this paper, the results of trapping carried out between November 2005 and October 2006, the population structure and the diseases of P. leniusculus inhabiting Brugneto Lake are analysed. The total sex ratio observed was 1:1.03 (males/females) and it did not differ significantly from the theoretical 1:1 value, whereas the sex ratio recorded during winter differed significantly from the theoretical value. The CPUE (Catch Per Unit Effort) calculated was significantly related both to mean seasonal temperature and water-level variations. Regarding diseases only the presence of chitinoclastic bacteria on exoskeleton were found. Branchiobdellidae (Annelida, Clitellata) were not observed either on the exoskeleton or in the branchialchambers, neither were ectocommensals, nor melanisation caused by bacterial infections on gill filaments. Fortunately, melanised spots on the legs usually caused by an infection of Aphanomyces astaci Schikora were not found. |
