Spatio-temporal density of the demersal Chondrichthyes assemblage in an upper bathyal of the eastern Mediterranean Sea

Abstract

Abstract Chondrichthyans are a very important taxon that plays a role at the top of the trophic level of the food chain and are vulnerable species in the marine ecosystem. The deep waters of the eastern Mediterranean Sea have been less studied than the continental shelf, especially for the chondrichthyans. Therefore, the present study was conducted to investigate the spatio-temporal distribution of chondrichthyans collected monthly in different depth strata (200–900 m) during different periods (2010–2011 and 2019–2021) using an otter bottom trawl. A total of 17 species were identified, consisting composed of 6 batoids, 10 sharks and 1 chiemaers was identified. The constant species (dominance: DO%> 50) in the study area were Galeus melastomus, Scyliorhinus canicula, Etmopterus spinax and Raja clavata. The most abundant species was E. spinax, followed by G. melastomus. There were 14 species in the first survey and 15 species in the second survey. Faunistic characteristics (number of species, abundance, diversity indices) varied only with bottom depth. Two different depthwise assemblages were estimated along the bottom depth gradient; ≤ 500 m and > 500 m. The discriminator species were R.clavata, S.canicula, G. melastomus, D. oxyrinchus and S. blainvillei found on the upper slope and E. spinax, G. melastomus and Centrophorus granulosus found on the lower slope. We estimated a total number of 26 species found in Antalya Bay, which was higher than the number reported in the previous studies.