Taxonomy of early life stages of anguilliforms in the northeastern mediterranean

The order Anguilliformes, commonly known as eels, is represented in the Mediterranean Sea by 25 species from 10 families, and in Turkish waters by 20 species. Taxonomic and ecological information on the larval stages of this group, known as leptocephali, is limited. In this study, preleptocephali and leptocephali belonging to Anguilliformes were examined using morphological and molecular methods, species identifications were conducted, and an identification key specific to the Eastern Mediterranean was developed. In addition, species abundance and distribution were investigated, findings on habitat preferences were presented, and the ecological importance of the Finike Seamounts for the early life stages of these species was evaluated. The study utilized anguilliform larvae collected during three research cruises: the Antalya Survey (2018–2019) with 35 stations, the Orkinos Survey (2021) with 97 stations, and the Finike Seamounts Survey (2024) with 60 stations. The Antalya Survey involved monthly sampling from depths of 0–100 m between June 2018 and June–November 2019. The Orkinos Survey in 2021 sampled ichthyoplankton from 0–30 m depths, while the Finike Survey in 2024 sampled from 0–200 m depths. Oblique ichthyoplankton tows were performed using Bongo-60 nets (200 and 500 µm mesh) during the Antalya Survey and Bongo-90 nets (500 µm mesh) during the Orkinos and Finike Seamounts Surveys. A total of 89 anguilliform individuals were obtained, including 22 eggs, six prelarvae, 30 preleptocephali, and 31 leptocephali. Detailed morphological analyses were performed on 46 preleptocephalus and leptocephalus individuals, and species identifications in seven specimens were confirmed using DNA barcoding, forming the basis for the identification key. The identified specimens belonged to four families: Chlopsidae (n = 3), Congridae (n = 25), Nemichthyidae (n = 16), and Ophichthyidae (n = 3). The findings provide a fundamental reference for the taxonomic identification of anguilliform larvae in the region. Furthermore, factors such as spawning and nursery habitat preferences of the identified species were evaluated from an ecological perspective. Keywords: Leptocephalus, Preleptocephalus, Finike Seamounts Special Environmental Protection Area, Ichthyoplankton, Ecology