Bycatch of Demersal Elasmobranchii in the Strait of Sicily

Fishing activities greatly threaten Elasmobranchii due to their vulnerable life-history traits. Elasmobranchii have been a common bycatch in the Mediterranean bottom trawling fleets since the 1970s, and most of them are listed as threatened owing to overexploitation by fisheries. The study aims to identify and estimate the number of rays and sharks caught by bottom trawling operating in the North sector of the Strait of Sicily, Central Mediterranean Sea. This area represents one of the most important fishing grounds for demersal species, exploited mainly by trawl fisheries where an important component of commercial and discarded bycatch comprises cartilaginous fishes. An assessment of the impact of trawl fishery on sharks and skates by examining bycatch recorded between 2009 and 2021 is provided. Zero-Inflated Negative Binomial (ZINB) Models were used to standardize catch data and predict the relative bycatch rates. The findings reveal that 13 rays and 8 sharks were caught during the monitoring period. Raja clavata and Raja miraletus are the most frequently captured rays, constituting around 13% and 10% of the total monitored hauls. Among sharks, Scyliorhinus canicula was the most frequently captured species, found in about 17% of the total monitored hauls, followed by Squalus blainville with approximately 8%. According to the International Union for Conservation of Nature Red List for the Mediterranean, among these 21 species, four are reported as Data Deficient, five Least Concern, six Near Threatened, three Vulnerable, four Endangered and one Critically Endangered. ZIBN outcomes indicate decreasing trends of CPUE of Rays while increasing trends are observed for Sharks. Information reported in this study is paramount to support management and conservation measures for these vulnerable species whose adoption is at an early stage in the Strait of Sicily.