The rising sea temperature is making tuna scarce off the coast of Southern Bolaang Mongondow district in the northern part of Indonesia’s Sulawesi island.
The sun was at its zenith but the blue sky over Southern Bolaang Mongondow district could only be seen here through gaps in the thick clouds. Most people would rest as the weather cools, but not Enik Tamulu.
The 48-year-old fisherman from Saibuah village in the Posigadan sub-district was busy loading his small canoe with equipment from his home not far away, with his wife.
Tamulu has been fishing in the sea for more than 30 years as his father was also a fisherman. Unlike other fishermen in the area, who fish for any fish, Tamulu focuses on tuna (Thaunnus thynnus) only.
That afternoon, Tamulu set out to hunt for the fish locally known as “Ikan Potong.” His wife and two children saw him off at the beach.
He needed five hours to reach the location where he usually catches tuna, a distance that easily gobbled up 30 liters of fuel. Sometimes, Tamulu meets other fellow fishermen on the way and exchanges information on any sighting of a school of tuna. He also exchanges information about the weather at their destination.
Catching tuna requires not only patience but also strength, especially since the fish are caught using traditional means — a fishing rod with nylon thread with a hook at its end. A sealed plastic bag containing small fish is dropped in the area to draw tunas.
The plastic would burst at a certain depth and draw tuna to the area.
Tamulu will stay on his boat for five days every time he sails to sea. However, it is also common for him to stay longer when the catch is small.
Catching tuna is not without risks and many fishermen have perished, victims of rough seas. Almost 50 fishermen have lost their lives at sea off Southern Bolaang Mongondow in the past five years, data from the district’s Disaster Mitigation Agency showed. A similar trend has been observed in neighboring districts.
Drifting at sea
In 2019, big waves hit his canoe, overturning it. Tamulu survived but drifted at sea for three days before being rescued by fishermen from Dudepo, another village about 80 kilometers from his own village.
At the time Tamulu was heading towards a raft that was quite far from his usual fishing location as after four days of fishing he had not yet made any catch. The sky was heavy with clouds and the sea swelled. Rain also greeted him as he approached Raft 8.
But a big wave hit his 13-year-old boat, overturning it and sending him and everything else to the sea. He floated holding onto an empty plastic jerrycan.
The mishap taught him to be more careful and avoid fishing when the weather is adverse.
At present, his fishing grounds are becoming farther and farther away and Tamulu has to shell out more money to pay for more fuel and food. Often, he also has to borrow money from fish collectors.
Besides the increasing distance, the tuna size was also becoming smaller, Tamulu said. He added this has resulted in dwindling income.
“Often, even though I caught fish, when I sold them I had to deduct the costs and my debt. I once fished for five days but after deducting the costs, I had only Rp 150,000,” he said.
With tuna getting increasingly difficult to catch and his income spiked, Tamulu was forced to take her daughter out of school — after year nine — as he couldn’t afford it anymore.
His eldest child, Ahmad, quit school to help his father fish. But Tamulu had never wanted to take his 18-year-old son fishing with him. He did not want to lose him at sea.
“No profit means our savings are depleted. Not only do we not have enough money to pay for the school’s costs, but it is also difficult to meet our daily needs,” Tamulu said.
Declining tuna catch in Southern Bolaang Mongondow
Dwindling fish catch is not just Tamalu’s problem. Almost all tuna fishermen off the shores of the Southern Bolaang Mongondow district encounter the same situation.
The local fishermen catch two types of tuna, thunnus obesus which is locally known as the bigeye tuna, and thunnus albacares, the yellowfin tuna known locally as tuna madidihang.
Data from the district fishery agency showed that the district’s tuna catch had dropped in years. In 2015, the tuna catch weighed 5,000 tons but in 2022 only 1,500 tons were caught.
Awaludin Lamaluta, head of the South Bolsel fisheries agency, explained that the figure is not exactly a benchmark for calculating tuna catch amounts in the district. However, the figure can be used to see the catch trend.
“We are working with tuna collectors across the district and the figure, as can be seen, continues to fall. There may, of course, be a few tons that escaped our data because some fishermen also directly sold their catch,” he said.
Lamalua said that extreme and irregular weather is the biggest factor behind the declining catch. The irregular weather also made fishermen think twice before fishing at sea.
The chart above reflects tuna catch in South Bolaang Mongondow district in 2015, 2019, and 2022 (ton).
Sea temperatures are also rising, contributing to the decline. Samuel Leivy Opa, a marine researcher and observer, said that the surface temperature of the sea had risen by one degree Celsius in the past few years.
The researcher who also heads the North Sulawesi Maritime Youth organization, said that the rising sea temperature impacted the marine organism and ecosystem behavior.
Tuna, he said, are nomadic and can travel long distances to find areas where the sea temperature suits them.
“They are swimmers. Tuna in our region can even swim to the Sea of Japan. They do not settle in any particular area. The rise in sea temperature can have an adverse impact because fish would no longer pass through areas where the sea temperature is already quite high,” said Opa.
In addition, Samuel also explained that the lack of fish that are the natural food of tuna is another factor in the reduction of the tuna population in one area.
“Tunas will certainly seek seas where they can find food. This food source gets scarce because of fishermen who catch fish on a large scale,” he said.
The sea temperature in the area now stands at 29 degrees while fish usually thrive in areas with 26 degrees temperatures.
“Our seas continue to rise in temperature, the marine ecosystem increasingly changes, there are many dying corals and this clearly has a really adverse impact,” Opa said.
The death of corals that are the habitat for small fishes will result in a chain of effects that affect other fishes, including Tuna.