The Chesapeake blue crab, Callinectes sapidus Rathbun, 1896: new finding, origin, and further spread in the Ukrainian part of the Black Sea

Biological invasions pose a significant threat to aquatic ecosystems, and the spread of uncontrolled non-indigenous species can have detrimental effects on biodiversity, ecosystem processes, and economic activities. The Chesapeake blue crab, Callinectes sapidus , native to the western Atlantic Ocean, is non-indigenous in the Black Sea region. This study presents novel findings on its presence and breeding in the Black Sea, particularly in North-Western part within the territorial confines of Ukraine. The study provides evidence of successful reproduction by a female blue crab with eggs in this non-native habitat, i.e. off the coast of Ukraine. Furthermore, molecular DNA barcoding analysis revealed the Ukrainian crab to be of a haplotype found in Italy and the United States, indicating potential connectivity between the Black Sea population and other established populations. Additionally, other haplotypes were detected in the Black Sea region, suggesting the possibility of multiple introductions and admixture between non-indigenous populations of different origins. The successful establishment and spread of C. sapidus in the Black Sea region may be attributed to its adaptability to a wide range of environmental conditions and the lack of natural predators or competitors in the invaded regions. This crab is commercialized in the USA, which may have implications for fisheries and aquaculture activities in Ukraine.