![]() However, we also found that differing assumptions as to the number and type of food web baselines and trophic discrimination factors led to differing estimates of trophic position in blue crabs at Gökçeada Island by as much as one to two trophic levels. We also observe that trophic position declined and the relative importance of pelagic carbon sources to blue crabs increased from April to August. In addition, the range of calculated trophic positions of blue crabs at Gökçeada Island (2.0 to 4.4), while broad, is in general agreement with prior studies in both native and non-native ranges. We found limited isotopic niche overlap between blue crabs and seven native species examined at Gökçeada Island in April, June, and August of 2017. The aim of this study was to provide a first assessment of the trophic ecology of non-native blue crab in the Northern Aegean Sea using stable carbon (δ13C) and nitrogen isotope (δ15N) analysis. ![]() Blue crabs in the Mediterranean Sea are of concern due to their presumed potential for negative consumptive and competitive interactions with native fauna. The Atlantic blue crab (Callinectes sapidus) was first recorded in the Mediterranean Sea in 1949, but may have arrived as early as in the 1930’s. Invasive non-native crustaceans are a biodiversity and management concern in the Mediterranean Sea. Ovigerous females have been observed between March and October and we have discussed related management issues including current fishery season. sapidus shred the nets and caused an economic loss. The results indicated that the species was mainly produced in the lagoons, whereas many coastal fishermen returned it as discard and 79% of fishermen emphasized that C. The maximum daily catch of blue crab in set nets showed a significant difference in the Levantine and Aegean coasts. sapidus has been seen in the Black Sea for the last decade. ![]() sapidus is commonly distributed along the Levantine and the southern Aegean coasts of Turkey, whilst it is rarely observed in the Sea of Marmara and the Black Sea. Responses were gathered from fishermen (n = 6) who fish in the lagoons and the head or members of fishery cooperatives (n = 104) in 28 cities, including the coastal regions of the Mediterranean Sea (Levantine), Aegean Sea, Sea of Marmara and the Black Sea in Turkey. Data were collected in 2020 by utilizing a telephone based questionnaire survey. This study provides information on the distribution and ecology of Callinectes sapidus in Turkey, as well as its maximum daily catch in set nets (trammel nets and gillnets), and its commercial fishery in lagoons.
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