Warm waters kill over $400,000 worth of fish

Fishermen haul up dead fish from the farms in Jeju, where a total of 231,000 flatfish in nine fish farms perished as of Monday due to rising water temperatures. [CHOI CHOONG-IL]

Around 360,000 fish perished in unusually warm waters recently, costing fish farms and fishermen an estimated 465 million won ($412,570) as of Monday evening.

The Ministry of Oceans and Fisheries said a total of 231,000 flatfish in nine fish farms in Jeju, 123,000 flatfish and starry flounders in 14 fish farms in Pohang, North Gyeongsang, and 8,000 flatfish in two farms in Busan died as of Monday. Their deaths are estimated to cost the farmers some 360 million won in Jeju, 88 million won in Pohang and 17 million won in Busan, the ministry said.

“Fish being cultivated in farms can die if the water temperature rises even one degree,” said Oh Tae-gi, an official of the Oceans Ministry. “The fish float some five to seven days after they die, so nearby fish farms are also likely to be affected.”

The National Institute of Fisheries Science issued a high water-temperature warning on Monday for waters off Wonsan Island in South Chungcheong and down south near Tongyeong, South Gyeongsang. It issued a high water-temperature advisory in the waters near Uljin County and Pohang, North Gyeongsang.

A high water-temperature advisory is issued when the water temperature reaches 28 degrees Celsius (82.4 degrees Fahrenheit) and a warning is issued when the water temperature reaches 28 degrees Celsius and does not drop for at least three days.

Flatfish need the water temperature to be 24 degrees Celsius or lower and starry flounder needs the water to be between 13 and 18 degrees Celsius. Many of the fish farms on land are operated by drawing seawater directly into the farms.

“In previous years, fish would die out in rising water temperature usually in mid-August,” said Kim Yong-bum, president of Daejung Fisheries Association in Jeju. “The water temperature rose this year earlier than we thought. We can fight rising water temperature by pumping in saline underground water, but this is not an option for many fish farms in the west coast of Jeju where no such pumping system has been installed.”

“The water temperature rose earlier in this season than it did last year, and we expect it to stay that way for a while,” said Han In-sung, researcher at the National Institute of Fisheries Science. “Because we expect the temperatures on land to hit at least 30 degrees Celsius for a while and there are no signs of a typhoon coming any time soon, the fisheries will have to brace for the worst.”

Offshore fish farms are also at risk, including those located near the Cheonsu Bay in South Chungcheong, where the water temperature rose from 23.5 degrees Celsius on July 1 to 28.5 degrees Celsius recently.

Some farm owners have hurriedly installed shades and liquefied oxygen tanks at the farms.

“Rockfish will die out in Cheonsu Bay if the water temperature stays above 28 degrees Celsius for more than a week,” said Lim Min-ho, director of the fisheries support department of the South Chungcheong provincial government. “In addition to the local governments’ assistance, the fishermen themselves need to take action and cooperate for the best results.”

The bay has some 8.36 million fish being cultivated in 112 farms as of last month. Rising water temperatures in Cheonsu Bay killed 5 million fish there in 2013, which cost the farm owners 5.3 billion won, and 3.77 million fish last year, which cost the owners some 5 billion won. A total of 13.56 million fish died in 369 fish farms across the country last year due to rising water temperatures, which cost the fishermen 18.3 billion won.

BY HWANG SUN-YOON, CHOI CHOONG-IL [chung.juhee@joongang.co.kr]