Biological traits, distribution patterns and spatial segregation of common and rare batoids in the North Aegean Sea, Greece

Elasmobranchs are among the most threatened marine taxonomic groups in the Mediterranean Sea. Moreover, knowledge of batoid life-history strategies and spatial distribution is limited, despite being essential to stock assessments and effective management. This study focuses on batoid species collected across the North Aegean Sea, Greece, from 2014 to 2021. Conversion factors and length at maturity were estimated to assess biological traits of batoids. Random forests and generalized additive models were used to detect underlying spatial distribution patterns of species occurrence and abundance, respectively. Overall, 3,920 specimens were measured from at least 13 species, with Rajiformes being the most common order, whereas Torpedo marmorata was the sole Torpediniformes recorded in the area. Females were larger than males in all species, and sizes at which 50% of fish reached maturity were among the lowest in the Mediterranean Sea. Predictions suggested that Dipturus oxyrinchus, Raja clavata and Raja polystigma had the broadest distribution, whereas Raja radula and Torpedo marmorata were found mostly in coastal waters. Additionally, only D. oxyrinchus was spatially segregated by sex, whereas spatial and bathymetric segregation was associated with ontogeny for Leucoraja naevus, R. clavata and R. polystigma. Our findings contribute to our understanding of the biology and behavioural patterns of batoid species in the North Aegean Sea and are of relevance to the development of conservation plans in the area.