Some aspects of population biology of the mud crab, Rhithropanopeus harrisii (Gould, 1841) in the Odra estuary, Poland

The mud crab is the only non-indigenous xanthid encountered in the River Odra estuary. In 2007-2008, the crabs were collected, using fish traps, to determine sex and to follow variations in individual weight and carapace length and width over a year. Sex-dependent differences in the crab morphometry were studied as well. The largest catch was that obtained in September (23.48% of the total number of 264 individuals) and October (31.82%). Male crabs accounted for 56.44% of the total number; males dominated in autumn (September-December) and spring (March, May, June) catches. Males showed significantly wider carapaces (16.81 ±3.98 mm; range: 5.60-22.90 mm) and mean individual weight (2.15 ±0.94 g; range: 0.15-3.93 g) than females (mean carapace width of 15.05 ±3.33 mm; range: 5.30-19.80 mm, and mean individual weight of 1.47 ±0.60 g; range: 0.13-2.56 g). Of the 11 morphometric characters analyzed, expressed in relative values (%), related to the carapace width, males showed significantly larger claw dimensions (CHL₁, CHW₁, CHH₁, CHL₂, CHW₂, CHH₂) and smaller abdomen widths (AW).