Distribution and diversity of elasmobranchs in the Sea of Marmara: A 2023 status report

Abstract

Abstract Elasmobranchs, encompassing an array of sharks and rays, confront a threat of extinction on a global scale. The Sea of Marmara (SoM) stands out as a critical refuge for these endangered species. This study harnesses data derived from comprehensive trawl surveys, representing the first area‐based evaluation of the elasmobranchs inhabiting the SoM. Sampling protocols were carried out at 10 separate stations along the 980‐km coastline of the SoM, each bounded by different ecological characteristics and anthropogenic influences. A total of eight shark species and six ray species were caught in the towed area of the entire the SoM. Notably, Scyliorhinus canicula and near‐threatened Raja clavata constitute more than 50% of the total abundance. Additionally, rare, and critically endangered species, including the Oxynotus centrina, Squatina squatina, Dipturus batis, and Myliobatis aquila, were documented, expanding our knowledge of their presence in the region. Spatial distribution heterogeneity was pronounced within species. Size distributions were species‐specific, and the presence of both juvenile and adult individuals suggested successful reproduction and growth. Records expand the known size range in the SoM for six shark and three ray species. It also provides first‐size information based on the total length of the S. stellaris and D. batis. Additionally, the urgent need for field‐based conservation efforts is highlighted, citing a previously unidentified important sensitive areas located in the southern part of the SoM.