Acoustic and net-based assessment of jellyfish distribution in the western Arctic Ocean during summer

Jellyfish play important ecological roles as both predators and prey and are sensitive indicators of environmental change. Rapid warming and sea ice loss in the western Arctic Ocean may be altering their distribution, yet traditional net sampling often underrepresents these fragile organisms. To address this, we combined non-destructive acoustic surveys with net sampling to investigate jellyfish spatial distribution in the East Siberian and Chukchi Seas from July 31 to August 22, 2024. Acoustic data were collected using a 38-kHz EK80 echosounder and analyzed with Echoview’s single target detection tool. Net sampling was conducted using vertically towed bongo nets (330 and 500 μm mesh) to 200 m depth. Key acoustic parameters—including echo number, target strength (TS, dB re 1 m−1), target depth, and range and depth variability (m)—were extracted. Jellyfish were primarily distributed at 40–75 m, with occasional occurrences at 120–180 m. Larger individuals (TS −75 dB) were typically found at greater depths. Jellyfish abundance was lowest in the southern Chukchi Sea and highest in the north, with regional differences in vertical distribution. These results demonstrate the utility of acoustic methods for monitoring jellyfish in polar environments and contribute to understanding their spatial patterns amid ongoing Arctic environmental change.