Seasonal changes in the distribution of black sea bream Acanthopagrus schlegelii estimated by environmental DNA

This study aimed at characterizing the distribution of black sea bream Acanthopagrus schlegelii , a major target fish of commercial and recreational fishing, using environmental DNA (eDNA). Twelve survey stations were aligned along an inshore-offshore axis in Tango Bay, southwestern Japan. Water samples were taken from the surface and bottom layers at each station monthly from May 2017 through April 2018 (twice in June 2017 and excluding October 2017). Quantitative polymerase chain reaction (qPCR) with species-specific primers and probe was used to detect DNA of black sea bream in water samples. Throughout the year, eDNA was abundant at inshore stations, especially at stations close to the river mouth in the innermost part of the bay. In May and June, eDNA was detected even at the most offshore station 19 km from the coast, whereas eDNA was detected exclusively within 3 km from the coastline during the months of July through April. The eDNA detected offshore in May and June were likely to have originated from eggs and/or larvae, as this species spawns pelagic eggs in early summer. These results through the use of eDNA indicated that black sea bream is highly dependent on coastal areas in its life history.