Rising East Sea temperatures linked to decline of cold-water dolphins

The National Institute of Fisheries Science said Monday that an analysis of cetacean sighting survey data collected in the East Sea since 2015 shows rising water temperatures are clearly altering dolphin distribution patterns.

A joint research team from the institute's Cetacean Research Institute and Keimyung University compared the distribution of six dolphin species commonly observed in the East Sea against satellite sea surface temperature data, confirming that the species fall into two distinct clusters — cold-water and warm-water groups.

According to the research, Pacific white-sided dolphins and Dall's porpoises favor cold waters averaging 11.6 degrees Celsius, while common dolphins, bottlenose dolphins, Risso's dolphins and false killer whales prefer warmer waters averaging 17.8 degrees Celsius.

The average spring (April–June) sea surface temperature along the East Sea coast rose from about 15 degrees Celsius in 2015 to about 17 degrees Celsius in 2024 — an increase of 2 degrees over a decade. In 2022 and 2024, when spring temperatures exceeded 17 degrees Celsius, no cold-water dolphins were observed.

Surveys conducted in March and May this year also found no cold-water dolphins, further supporting the conclusion that rising East Sea temperatures are directly affecting dolphin distribution.

Kwon Soon-wook, director of the institute, said the findings represent "an important case showing the impact of climate change on our marine ecosystem," adding that the institute would "do its utmost to closely analyze changes in the marine ecosystem through systematic surveys and research, and to build a scientific foundation for the conservation of marine mammals."