Biological parameters and spatial segregation patterns in sharks from the North Aegean Sea, Greece

Abstract

Context Sharks are frequently caught as bycatch in trawl fisheries in the North Aegean Sea. However, very little information exists on their biology and ecology in the area. Aims Biological parameters and spatial segregation of sharks in relation to size class, sex, depth and geographic location were examined. Methods Morphological characteristics and generalised additive models were used to explore biological traits and aggregating behaviour respectively, by using data from the Mediterranean International Trawl Survey between 2014 and 2021. Key results Overall, 7761 specimens were measured, with Scyliorhinus canicula, Galeus melastomus and Squalus blainville being the most common species. Scyliorhinus canicula was found in shallow coastal waters, whereas the remaining species were detected in deeper waters. Conclusions Females were larger and heavier than males and the weight–length relationships corroborated size differences between sexes in all species, whereas allometric growth did not share the same patterns as those from the Mediterranean Sea. Generalised additive models showed that the distribution of dominant species is bathymetric and geographically dependent. Additionally, the depth and geographic segregation patterns are highly associated with ontogeny and not sex. Implications These findings highlighted the importance of incorporating elasmobranch behavioural characteristics in the poorly developed management regulations in the North Aegean Sea.