▲ A fisherman installs a shading net to block the intense sunlight at a rockfish and red seabream cage fish farm near Junghwa Port, Sanyang-eup, Tongyeong, South Gyeongsang Province, on the morning of August 4. (Photo: Yonhap News)
"This is the worst heatwave ever, and if water temperatures rise, it's game over. Fishermen are on high alert for fear of mass fish mortality caused by high water temperatures."
Around 11:00 AM yesterday (August 4), a 0.75-hectare cage fish farm was reached after a roughly five-minute boat ride across the azure blue waters from Junghwa Port in Sanyang-eup, Tongyeong, South Gyeongsang Province.
At the site, where the air temperature hit 33°C (91°F), a 57-year-old fisherman surnamed Lee was sweating profusely while intently covering the surface of the farm with shading nets to block the scorching sunlight.
These shading nets are polyester-based, net-like covers designed to block solar radiation.
"With the weather already so hot and the sun beating straight down on the fish farm, we have to cover it with shading nets to prevent water temperatures from rising," Lee said.
According to South Gyeongsang Province, a high water temperature advisory has been in effect since July 27 for coastal waters including the area between the western end of Yokjido Island and the eastern end of Bijindo Island, which encompasses Sanyang-eup in Tongyeong.
A high water temperature advisory is issued when water temperatures reach 28°C (82°F) or are expected to do so.
While damage from high water temperatures has not yet occurred in earnest, fishermen like Lee are pouring all their efforts into preventive measures following the issuance of the advisory.
Lee, who farms about 400,000 rockfish and about 90,000 red seabream, manages his farm fully equipped with a hat, mask, rubber boots, and long-sleeved clothing every day to shield himself from the scorching sun on the open sea devoid of any shade.
He sweats like rain every time he goes out to and returns from the fish farm.
"While full-scale damage from high water temperatures hasn't appeared yet, once it happens, there are no countermeasures, so we have no choice but to focus on advance preparations," Lee explained, adding, "I check the temperature of the sea around the farm at every opportunity."
He added, "Right now, there is a cold water mass phenomenon (where a mass of cold water from the deep sea temporarily moves to the surface), but water temperatures could rise sharply later. In times like this, we double up on the shading nets."
Among farmed fish, red seabream manage to endure high water temperatures relatively well, but rockfish react sensitively to the heat.
Once mass mortality begins due to high water temperatures, the damage spirals out of control.
Because of this, Lee, who is also enrolled in fishery disaster insurance, sold off about 70,000 rockfish early to the market last June, right before the full-fledged heatwave arrived.
While working on putting up the shading nets on this day, he fed a school of rockfish that had not been fed in the morning.
Even after the feed was scattered across the water, the rockfish slowly rose to the surface, their movements seemingly slowed by the heat.
"In the summer, the fish get stressed, lose their appetite, and can't even eat properly," Lee said, clicking his tongue.
Around 11:00 AM that day, the surface water temperature around Lee's fish farm was recorded at 21.3°C (70°F).
Considering that the optimal water temperature for rockfish growth listed in the "Rockfish Farming Standard Manual" by the National Institute of Fisheries Science under the Ministry of Oceans and Fisheries is 15 to 18°C (59 to 64°F), the local waters are already quite warm.
Given this situation, Lee's concerns run deep.
"This year's summer is unusually hot, and considering that high water temperature damage typically begins around August 10, I can't help but worry even more about what's ahead," he emphasized.
(Photo: Yonhap News)
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