Evaluation and comparison of fishing gears for the capture, management, and control of the invasive blue crab in a Mediterranean coastal area

Following the unprecedented blue crab (Callinectes sapidus Rathbun, 1896) outbreak in the Northern Adriatic during 2023 and the local lack of knowledge on its fishery, this study tested different types of fishing gears to compare their effectiveness in catching the species. The tested gears included the traditional fyke nets, locally called "tresse con bertovelli" and four types of crab pots, with either single or double chamber, some produced locally specifically for blue crab capture. Efficiency (defined as the probability of catching blue crabs when present), yield (catch per unit effort), species selectivity, size selectivity and sex selectivity (assessed as the proportion of each category over total catches) were evaluated. Results indicated that both the double chamber pot (inspired by North American designs) and the local fyke nets were the most effective gears overall in terms of efficiency and yield. However, the double chamber pot demonstrated significantly higher species selectivity in the capture of the blue crab, with lower bycatch of the native green crab (Carcinus aestuarii Nardo, 1847), and a greater size selectivity, targeting larger, adult specimens of blue crab. Conversely, fyke nets and smaller pots showed lower blue crab selectivity and a higher catch of green crabs and juvenile blue crabs. We conclude that the double chamber pot is the most suitable gear for managing or commercially exploiting the invasive blue crab population, offering high yield and species and size selectivity, thereby minimizing potential bycatch impacts on traditional fisheries. The results of this study could be helpful for managing the species, reducing its negative impacts and potentially exploiting it more effectively.