Invasion of freshwater systems by the Atlantic blue crab Callinectes sapidus Rathbun, 1896 – new insights from Italian regions

Abstract

The Atlantic Blue Crab, Callinectes sapidus Rathbun 1896, is a highly invasive species in the Mediterranean Sea, posing significant ecological and socio-economic threats in marine and estuarine environments. This study examines the presence and potential impact of C. sapidus in Italian inland waters, focusing on specimens collected from an irrigation canal of Pomposa along the Adriatic coast, and the Ombrone River which flows in the Tyrrhenian Sea. The morphometric analysis revealed that males from Pomposa had a mean carapace width (CW) of 172.15 mm (SD = 23.77 mm) and a mean weight of 282.10 g (SD = 98.34 g), while females had a mean CW of 160.68 mm (SD = 25.76 mm) and a mean weight of 173.26 g (SD = 56.11 g). In contrast, males from the Ombrone River were significantly smaller with a mean CW of 73.36 mm (SD = 10.11 mm) and a mean weight of 25.33 g (SD = 8.86 g). The sex ratio in Pomposa was heavily skewed towards males (3.26:1), indicating dominance of adult males in freshwater systems. In the Ombrone River there was a similar situation, although the smaller size of the sample: out of a total of 10 specimens, only 1 was female. The condition factor (K) was significantly higher for females (1.960) compared to males (0.116). The growth coefficient (b) differed between sexes, with males exhibiting a higher value (2.401) compared to females (1.788), indicating different growth patterns. This study provides new ecological and biological data on C. sapidus in freshwater systems, and underscores the need for targeted monitoring and management strategies to mitigate the spread and impact of this invasive species in Italian inland waters.