Ulleung Island's fishers struggle as East Sea waters warm

Social Affairs

Published: 03 Oct. 2023, 17:49

Ulleung Island's fishers struggle as East Sea waters warm

The JoongAng Ilbo's special reporting team and researchers at the Korea Institute of Ocean Science and Technology (Kiost) swim and search in the ocean near Ulleung Island. [JOONGANG PHOTO]

Intensified global warming is sparking unprecedented weather phenomena across the globe, and Korea's East Sea has proven no exception.

The ocean serves as a carbon sink, absorbing the carbon dioxide emitted by humans, and also plays the role of a refrigerator, absorbing the heat of our warming planet.
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Under the accelerating impact of climate change, the East Sea's marine ecosystems have been collapsing, and the ocean is facing a crisis where it may lose its inherent carbon storage capacity.

According to 65-year-old Kim Hae-su, who has been catching squid in the waters off Ulleung Island for 42 years, squids were very hard to come by this year.

“Yesterday, I caught about five, but today, I didn't even see any,” Kim told the JoongAng Ilbo at Ulleung harbor on Aug. 15.

The aging fisherman had been noticing the changes in the sea.

The high sea temperatures, reaching up to 30 degrees Celsius (86 degrees Fahrenheit), were driving away the schools of squid that mainly inhabit the point where warm and cold currents meet. He said the squid needed for the Ulleungdo Squid Festival, which was starting the next day, had to be brought from distant seas. Kim said.

“I've seen the squid catch decreasing rapidly for the past five to six years,” Kim said.

“I have no other skills besides this, so I'm worried about how I'll make a living.”

A bird's eye view of Ulleung Island [KIOST]

The decline in squid around Ulleungdo in recent years has been due to the warming of the East Sea.

This year, global sea surface temperatures have reached unprecedented levels due to climate change and the development of El Niño.

The East Sea is considered an unusually hot spot with high sea temperatures.

According to the analysis of East Sea temperature data from NOAA satellites conducted by Oceanography Professor Kim Il-nam's team at Incheon National University, this summer saw the highest occurrence of “marine heatwaves,” which refers to a phenomenon of prolonged high temperatures in the top 10 percent of average sea surface temperatures.

According to Kim's team, the average number of days of marine heatwaves in the East Sea this summer was 54.1 days, compared to just 1.6 days in the first year of observation in 1982.

The number of days of marine heatwaves was around 50 days per year a decade ago. This rose to 129 days last year, and this year, there were 54 days in summer alone.

“The East Sea is where the boundary between the cold water of the north and the warm water of the south is formed. Due to global warming, the warmer water from the south is flowing in more strongly, leading to a more pronounced increase in marine heatwaves,” Kim said.

Accelerating global warming is transforming the East Sea and Ulleungdo.

Ulleungdo, often referred to as the “Galapagos Island of Korea,” is known for its rich biodiversity due to its location at the convergence of cold and warm currents. However, this also makes it highly sensitive to climate change.

The JoongAng Ilbo’s special reporting team joined a research team from the Korea Institute of Ocean Science and Technology (Kiost) on an underwater survey on climate change on Aug. 13, diving beneath the waves.

The sea temperature was 29 degrees Celsius, and even underwater, the heat was palpable. Even at a depth of 18 meters, the water temperature was still 26 degrees Celsius, and tropical fish typical of tropical seas, such as parrotfish, appeared before the reporters’ eyes.

Seaweed known as umibudo in Japan, also known as sea grapes, covered the seabed.

Caulerpa, a species of green algae, spreads underwater near Ulleung Island. [KIOST]

Dr. Min Won-ki of the Kiost said, “The numbers of giant horned turban and abalone, which can be seen in temperate regions, have been decreasing, and there's a recent trend toward algae that prefer tropical conditions like umibudo appearing. Unprecedented tropical species are also appearing around Ulleungdo and Dokdo.”

In fact, the past three years have seen the discovery of the spotted unicornfish, a species living in tropical seas, in the waters off Ulleungdo for the first time.

“I've been fishing for a long time, but this is the first time I've seen such a fish. It seems to have come from the south due to the rising sea temperature,” fisherman Jeong Yoo-gwan, 64, said.

“Even captains who have not left their boats for more than 40 years were surprised to see such a fish.”

The changes have disrupted the harmony of the Ulleungdo waterfront, with the squid catch — which used to be the main source of income for fishermen — having decreased by 93 percent compared to 30 years ago.

Last year's catch was only 978 tons out of the 14,000 tons caught in the past, and this year's catch is only one eight of last year's during the same period.

“Not only is the quantity of squid caught low, but the size of the squid caught is smaller than last year, so the actual sales are only about 10 percent of the same period last year,” said Lee Ju-won, head of the Ulleungdo Fishermen's Association

Kim Yun-bae, who oversees operations at the Ulleungdo·Dokdo Ocean Science Station of the Korea Institute of Ocean Science and Technology, said, “The squid fishing grounds are where the warm and cold currents intersect, creating the right sea temperature and, more importantly, forming a food chain. With the strong influx of warm currents from the south, extreme high-temperature phenomena have begun to appear around Ulleungdo and Dokdo, changing the fishing grounds.”

The threat of marine heatwaves is not the only issue.

A spotted unicornfish was found in the oceans around Ulleung Island. [RESIDENT OF ULLEUNG ISLAND]

Warmer seawater, which absorbs heat, accelerates the rise in sea levels. Over the past 30 years, the sea level around Ulleungdo and Dokdo has risen by 6.17 millimeters per year, which is about twice as fast as the overall average in the Yellow, South, and East Seas.

Warmer seawater supplying more moisture and energy also leads to increased damage from extreme weather such as typhoons and heavy rains.

At Sadong Harbor, the remains of a breakwater that collapsed due to record-high waves during Typhoon Maesak three years ago, were still seen.

“When the balance of the marine ecosystem is disturbed, it signals the beginning of a collapse, and marine heatwaves are a sign that we've reached that threshold,” Kim said.

He expressed concern that disasters such as extreme weather events like typhoons would accelerate significantly in islands and coastal regions.

A research team from the National Institute of Fisheries Science recently analyzed plankton samples collected from the East Sea between 2018 and 2020. The results showed that plankton sizes have become smaller compared to the past.

“Plankton, which relies on photosynthesis using light, needs to be in the surface layer, and nutrients from the lower layer need to rise,” Youn Seok-hyun, a researcher at the National Institute of Fisheries Science said.

“With the reduced supply of nutrients rising from the lower layer, it appears that there are more micro-sized plankton that can survive under relatively unfavorable conditions.”

The shrinking of phytoplankton, the most important source of energy in marine ecosystems, affects the entire food chain, including zooplankton and fish, leading to a decline in marine productivity.

According to the National Institute of Fisheries Science, the productivity of the East Sea has declined by about 38 percent over the past five years compared to 20 to 30 years ago.

“If climate change continues to accelerate, the East Sea could become like the tropical seas of equatorial regions, with less visible phytoplankton and nutrients, making it more transparent,” Kim from Incheon National University said.

BY CHON KWON-PIL [cho.jungwoo1@joongang.co.kr]