Environmental DNA metabarcoding complements bottom trawling and detects fish species beyond recorded ranges in the...

Global climate change is profoundly altering Arctic marine biodiversity, yet baseline data on fish assemblages in the central Arctic Ocean remain critically scarce. The Chukchi Borderland-a Pacific-Atlantic water confluence zone experiencing the most pronounced sea ice retreat in the Arctic-is a frontline area for assessing fish diversity dynamics under climate change. In this study, we simultaneously conducted bottom trawling and environmental DNA (eDNA) metabarcoding to evaluate their complementarity in characterizing fish diversity and to detect species beyond their previously documented ranges. Trawling at 16 stations captured 72 specimens from 17 species, while eDNA metabarcoding of 69 seawater and sediment samples from 31 stations detected 16 species, of which only two were shared with the trawls, highlighting their complementarity. The detected taxa-including pelagic groups (Myctophidae, Gadidae) and demersal groups (Cottidae, Zoarcidae)-align with the region's biogeographic character. Log-transformed eDNA sequence reads were strongly correlated with species' site occurrence frequency, validating the site-occurrence model for inferring relative abundance in Arctic waters. Notably, six species-Artediellus atlanticus, Lycodes raridens, Zaprora silenus, and the Atlantic-affiliated Lycodes lavalaei, Lycodes gracilis, and Hippoglossoides platessoides-were detected beyond their historically recorded northern boundaries. We interpret these signals cautiously: they may reflect climate-driven northward expansions, but may equally indicate historically under-sampled resident populations given the extreme paucity of baseline surveys in the central Arctic Ocean. This study provides the first paired comparison of eDNA and trawling in the central Arctic Ocean and delivers new evidence essential for filling ecological baseline gaps in this rapidly changing region.