Integrated analysis of trophic structure and feeding dynamics of invasive Callinectes sapidus Rathbun, 1896 in a Mediterranean coastal lagoon using stable isotopes and digestive enzyme activity

The objective of this study is to examine the invasive characteristics of the blue crab (Callinectes sapidus Rathbun, 1896) and its potential impact on lagoon ecosystems. A total of 90 individuals were collected from the Çanakkale Strait. A comprehensive suite of analytical techniques was employed, encompassing stomach content analysis, stable isotope analysis, and digestive enzyme profiling. The resulting data set was then subjected to rigorous statistical and bioinformatic analysis, with a particular focus on elucidating its correlation with morphometric characteristics. Stomach content analysis revealed that algae (47.19 %) and fish (25.37 %) constituted the primary dietary components. Isotope data further confirmed the species' omnivorous feeding strategy, with Ruditapes decussatus emerging as a dominant dietary component in isotopic signatures, although it was not directly observed in stomach contents. Adult male specimens exhibited a propensity for carnivorous feeding behaviour, as evidenced by isotopic patterns, which may be indicative of vestiges of their pelagic larval phase. A dietary niche overlap was identified between C. sapidus and the native green crab (Carcinus aestuarii) in the lagoon, with the former exhibiting a broader niche width. Despite the limited sample size, these findings contribute valuable preliminary insights into the feeding ecology and ecological interactions of C. sapidus in Mediterranean transitional waters, highlighting its potential invasive impact.