Deaths of farmed fish from high water temperatures are spreading along the southern coast of Gyeongsangnam-do Province, and a red tide alert has been upgraded in the same waters, raising concerns that damage to the fishing industry will widen.
More Than 3 Million Fish Dead as Heat and Red Tide Compound Damage
Provincial authorities said on the 28th that farmed fish deaths rose by 714,000 in a single day the previous day, while an additional 170 strings of farmed sea squirt also died. That brought cumulative losses this summer to 3.031 million farmed fish and 570 strings of sea squirt.
At 122 offshore cage and land-based farms across four municipalities — Namhae-gun, Hadong-gun, Tongyeong and Geoje — losses included 2.538 million Korean rockfish, 210,000 mullet, 195,000 dark-banded rockfish, 67,000 filefish, 13,000 starry flounder and 570 strings of sea squirt. The damage is estimated at 6.14 billion won.
Under the standards of the National Institute of Fisheries Science, a high-water-temperature advisory is issued when the water reaches 28 degrees Celsius, and a warning takes effect if the condition persists for three days or more. A high-water-temperature warning remains in place across all waters off the southern coast of Gyeongsangnam-do.
Preliminary readings the previous day showed water temperatures of 28.1 to 30.5 degrees in Sacheon Bay and Gangjin Bay, and 28.8 to 29.7 degrees in Jinhae Bay.
Red tide, which had been subdued through July and August, is also gathering strength again. The National Institute of Fisheries Science upgraded a preliminary red tide alert to an advisory at 4 p.m. on the 27th for waters from the west of Dumido Island to the west of Bijindo Island off Tongyeong. It also issued a new red tide advisory for waters from the west of Bijindo Island to the east of Jisimdo Island off Geoje.
Oceans Warming Worldwide, and Twice as Fast Around the Korean Peninsula
The unusual heat in the waters off Gyeongsangnam-do is not a local phenomenon confined to the southern coast. Experts agree it is unfolding within a broader trend of warming across the world's oceans.
According to the European Union's Copernicus Climate Change Service, the average daily sea surface temperature across the world's oceans between 60 degrees south and 60 degrees north reached 21.10 degrees Celsius on the 22nd. That surpassed the previous record of 21.09 degrees set in March 2024, and marks the highest reading in about 47 years, since satellite observation began in 1979.
Global sea surface temperatures typically peak for the year in March or April, as summer ends in the Southern Hemisphere. This year the peak came far later, in August. A strong El Nino is cited as the main factor. In a seasonal outlook released on the 31st of last month, the World Meteorological Organization projected that El Nino would strengthen further between August and October and peak around November.
The trend is more pronounced in waters around the Korean Peninsula. According to the 2026 Climate Change Impact Briefing Book for the Marine and Fisheries Sector, published this year by the National Institute of Fisheries Science, surface water temperatures around Korea rose 1.60 degrees over the 58 years from 1968 to 2025. That is about twice the global average increase of 0.76 degrees over the same period.
The Korea Meteorological Administration forecast that sea surface temperatures in waters around Korea would continue rising from September through November, with a high likelihood of developing into a strong El Nino. Observers say the combined burden of high water temperatures and red tide off the southern coast of Gyeongsangnam-do could persist for some time.
