A comparative analysis of two allochthonous populations of the Chinese mitten crab (Eriocheir sinensis H. Milne-Edwards, 1853) from the Szczecin Lagoon (NW Poland) and San Francisco Bay (US West coast)

Selected biological and morphometric characters of two populations of the nonindigenous Chinese mitten crab,one from the Szczecin Lagoon (SL) and the other from San Francisco Bay (SFB),b oth sampled in autumn, were analysed. The SL crabs showed a significantly higher individual weight,l ength and carapace width. Males accounted for 55% (87 individuals) of the 179 SL crabs,an d 62.9% (90 individuals) of the SFB crabs. Statistical analysis of metric characters,expr essed as a percentage of carapace width (X2),en abled four diagnostic characters to be identified: abdomen width (X11),carapace height (X3),left claw length (X7) and carapace length (X1). These jointly explain 71.75% of the differences between the SL and SFB crabs and are indicative of the distinctness of the populations.