Warming seas slash Ulleung's squid catch by 99 percent in 25 years

The squid catch around Ulleung Island has plummeted amid rising sea temperatures caused by climate change, highlighting how warming waters are reshaping Korea’s marine ecosystem and the coastal communities that depend on it.

According to Ulleung County on Sunday, the local catch fell from 11,315 tons in 2000 to 1,852 tons in 2015 and 1,172 tons in 2020, before plunging to 141 tons in 2025.

The 2025 catch amounted to just 1.2 percent of the 2000 figure. The decline has continued this year, with only 54 tons caught from January to September. Squid is the signature seafood of the island in North Gyeongsang Province and has long been a mainstay of its economy.

The decline stems largely from rising sea temperatures, which have reshuffled the marine food chain and are pushing squid out of Korean waters.

The National Institute of Fisheries Science (NIFS) believes squid that would normally grow off Korea’s coast have moved north toward Russia and other areas as their main coastal and offshore habitat in the southern East Sea has warmed.

The average sea surface temperature around the Korean Peninsula from January to June this year was 17.17 degrees Celsius, the highest level in 26 years. That marks an increase of 1.17 degrees from last year and 0.52 degrees from the previous record set in 2020, according to NIFS.

Along the east coast, the average sea surface temperature from April to June this year rose 1.9 degrees from last year to 16.3 degrees Celsius.

The sharp drop in Ulleung’s squid catch has fueled calls for the island to farm new high-value species to replace squid. Last month, the county began farming goldeye rockfish as a potential alternative, though only as a pilot project. It has also tried farming shrimp, red sea cucumber and Korean rockfish, among others, but none has yet become established enough to fill the gap.

“Finding new sources of income is important as local fisheries struggle with climate change and a shrinking squid catch,” Ulleung County Mayor Nam Han-kwon said.

The sharp decline in squid catch on the island is the latest example of how rising water temperatures are transforming Korea’s seas. Shark sightings off Korea's east coast have nearly quadrupled this year as climate change pushes more of the predators into Korean waters.

According to NIFS, 46 large sharks were spotted off the east coast from January to June this year, compared with 12 in the same period last year. Shortfin mako sharks, rated "high" for the risk of attack in the agency's shark classification guide, were the most common, with 23 sightings.

The surge in shark sightings tracks a broader warming trend in Korean waters. As temperatures climb, warm-water fish move further north along the east coast, and the large sharks that prey on them follow.