Species-specific detection of saffron cod (Eleginus gracilis) eDNA in the Bering and Chukchi seas during the MR20-05C research cruise

To provide an overview of the distribution of saffron cod (Eleginus gracilis) in the Bering and Chukchi Seas, environmental DNA (eDNA) of saffron cod was analyzed using a novel species-specific assay. eDNA samples were collected during the MR20-05C cruise conducted by the 'R/V Mirai' of Japan Agency for Marine-Earth Science and Technology. For eDNA sampling, surface seawater was collected and filtered through a cartridge filter (Sterivex HV, 0.45 m pore size; Millipore, Burlington, MA, USA). Additionally, eDNA samples were obtained from seawater collected at the middle or bottom layer using a Niskin water sampler in the same manner. We designed a species-specific quantitative real-time PCR (qPCR) TaqMan assay that targets the cytochrome b region of mitochondrial DNA to detect specifically saffron cod eDNA. This assay was used to detect and quantify saffron cod DNA in the samples.