Jellyfish War | A Marine Crisis

A round object floats silently in the distance. It is a brown-banded moon jellyfish that usually inhabits cold sea waters. At some point, swarms of jellyfish began to appear frequently off the coast of Korea. Some jellyfish are as large as a beach umbrella. Once rarely sighted in Korea, jellyfish have now become unwelcome creatures in the fishing industry. It has grown into a crisis that has overwhelmed fishing communities. Most of the fish that are hauled in are dead after being stung by jellyfish. Fishermen find it impossible to bring in a decent catch. How are these swarms of jellyfish impacting the shores of Korea? Spring has arrived in March. Marine plants flourish under the sea, while on land, plants have not awakened yet. But other sea creatures abound in the ocean besides marine plants. Like growing phantoms, Spiracodon saltatrix jellyfish move along with the sea currents. They patiently wait for food. Around this time of year, Neomyces intermedia are abundant in the ocean. The jellyfish silently hunt these tiny creatures. They kill their prey in seconds. Its silk-like, venom-filled tentacles paralyze prey instantly. Although it appears to be willowy and weak, Spiracodon saltatrix is an efficient assassin with a venomous sting. In March, sea temperatures drop to their lowest levels of the year. Here we see a brown-banded moon jellyfish. This colorful jellyfish appears briefly in these waters until water temperatures rise again. Following the sea currents, jellyfish are nomadic creatures. The only obstacles they occasionally face are fish nets. Due to their size and slow reaction, they easily get tangled in nets. Its fate is sealed once it gets caught in a net, but it also creates headaches for fishermen. Young Gil Hwan is a fisherman in Semangun Bay, North Jolla Province. He looks at the ocean below with concern. A huge swarm of moon jellyfish floats around the boat. These jellyfish swarms are a nuisance to fishermen, who depend on their daily catch to make a living. It's blue crab season, but their nets only haul in jellyfish after jellyfish. Moon jellyfish have a tough body, making it difficult for the fishermen to pluck them out of the nets. Jellyfish have existed on earth for 500 million years, long before the appearance of humans. The jellyfish population has grown astoundingly recently, and fishermen now despise them as ocean pests. Nearly every fisherman has suffered losses due to jellyfish. Due to the strong sea currents, the fishermen have to monitor their nets, or else the sheer weight of a jellyfish swarm can break through a net. In order to prevent this, the fishermen repeatedly cast and haul in their nets. But even then, they catch more jellyfish than fish. The fish are crushed to death by the heavier jellyfish, so the fishermen have no choice but to salvage any live fish they can find. The fishermen look on in despair. The boat's captain is at a loss for words. He dumps the catch off the boat with a water hose. The seagulls gorge on the dead fish floating on the surface. Most fishing boats look for areas where there are no jellyfish, instead of looking for a school of fish. The fishermen toiled all night. On the following morning, dead jellyfish are scattered on the beach due to a low tide. Unable to ride the tide, these jellyfish became stranded here. Their numbers are an indication of how active they were at night. However, this is just the beginning. Soaring waves churn the ocean below. Something is occurring underneath the surface. Plankton, sea squirt, and salps appear in huge numbers. Visibility deteriorates as these creatures spawn eggs nearly simultaneously. The ocean environment is altered in minutes. This continues throughout the night. These pollen-like specks are zooplankton. Seahorses appear amidst the colorful plankton. Seahorses inhabit tropical waters, but they are now sighted off the coasts of Korea due to rising water temperatures. Predators hunt at night. This coral extends feathery-like strings. It uses them to trap the tiny plankton. It feasts on the plankton all night. Hidden in a crevice, this North Pacific giant octopus is another large predator. As a feared sea predator, the octopus throws its entire body onto a prey when hunting. After three attempts, the octopus nabs a conger eel. It's a lucky day for the octopus. But the eel counterattacks when the octopus lets its guard down. The eel clamps its teeth on the octopus's vulnerable spot. The tables are turned. The octopus has to fend off the attack and get away. After struggling for five minutes, the octopus suffers an injury. The eel bit off a piece of its flesh. Still not in the clear, the eel tightens its grip on the octopus's leg. Few creatures can overpower a North Pacific giant octopus. It uses its suction cups. Attaching its suction cups on the eel's entire body, it suffocates the eel by closing its mouth shut. The deadly struggle ends quickly. Carrying its dead prey, the octopus disappears into the sea. July is a season of abundance in the ocean. Plankton thrive in warmer water temperatures, and the fish that feed on them swiftly multiply in numbers. But an ominous shadow also appears around this time. A swarm of Numuras jellyfish are spotted near the ocean surface. This species is rather large and highly venomous. They also appear in swarms, inflicting more damage to fishermen. In the last eight years, the population of Numuras jellyfish has risen dramatically. But where do they come from? The National Fisheries Research and Development Institute's exploration ship heads southward from Jeju Island. Experts believe that the area is the spawning area for Numuras jellyfish. As expected, they encounter Numuras jellyfish. Korea has recently begun studying this specimen. First, the scientists have to determine if this red jellyfish is identical to the Numuras jellyfish that have appeared in Korea. If they can discover the spawning grounds of these species, they can learn much more about their life cycle. But the specimen is smaller than an adult Numuras jellyfish. Numuras jellyfish are the closest species to the North China Sea. That's why they are so small. But compared to them, the ones in the South and the West Sea are much larger. They are moving and growing. The researchers learn that it takes about 15 days for the jellyfish to reach the coasts of Jeju from their spawning grounds. For 15 days, the jellyfish eat about 500,000 jellyfish at a time and reach the coasts of Jeju. The waters around Chujado Island are the sea route that the Numuras jellyfish take every year. A raft is lured to the ocean so that divers can record underwater footage. Floating objects take the diver by surprise. An endless swarm of Numuras jellyfish appear. They move together to cover a long distance. While riding the ocean current, they have fattened themselves, becoming more menacing to their prey. How do jellyfish digest food? Jellyfish have countless tiny holes on their bodies. The two-millimeter-wide holes voraciously suck in plankton. So, most of the plankton drifting in the ocean are eaten by jellyfish, which leaves less food for fish. Recently spawned fry are dependent on plankton for food, but now they have to compete against jellyfish to survive. Aggravating this imbalance is the fact that jellyfish also eat fish eggs. The survival of fish depends on their ability to thwart the voracious appetite of jellyfish. But why are jellyfish coming to Korea's shores? Due to overfishing, fish populations have plummeted, giving jellyfish less competition for food. Furthermore, the rise in water temperatures have boosted the population of plankton, creating ideal conditions for jellyfish. Uljin is a city that is located along the shores of the East Sea. This sleepy fishing village is under siege due to the appearance of swarms of Nomura's jellyfish. Swarms of jellyfish get tangled in the fixed shore net fishing grounds. The fishermen laid a two-kilometer net in the ocean to lead schools of fish towards the shores. A Nomura's jellyfish floats along the wide mesh net. Most creatures can easily slip through the nets, but most adult Nomura's jellyfish can grow as large as two meters in width and end up getting tangled in these nets. Quite a few of the jellyfish are already dead. The surviving jellyfish struggle to disentangle themselves, while others continue to search for a way out. These two jellyfish got lucky. They discovered a hole. The lucky jellyfish dances away towards the open ocean, along the shores of Jangja-do-ri, Gunsan. Giant jellyfish cause great damage to fishermen in the area. But they invented an ingenious net that separates the jellyfish from the fish. Giant jellyfish have encroached on this tiny island village. Unable to extract the jellyfish from the water, he lets it escape. When the sun sets, Mr. Kim sets sail to fish in the dark. Anchovies are usually caught at night. All fishermen wish for a large catch. Whenever they haul in their nets, they hope for the best. The small jellyfish that Mr. Kim mentioned earlier turns out to be translucent moon jellyfish. They have to be separated from the catch quickly, or else they'll crush the anchovies to death. But this is actually a good day for Mr. Kim. This nuclear power plant is located in Uljin, North Gyeongsang Province. The growing numbers of jellyfish have created an emergency situation. Jellyfish are drawn into the intake pipes of the power plant. Nets are cast around the intake holes to keep jellyfish away. However, the nets are on the verge of bursting. The nets have to be replaced constantly before they reach their breaking point. There's even a division that is dedicated to monitoring jellyfish swarms. At times like this, we catch up to 100 tons a day. Several times a day, the men have to replace the nets with new ones, or else the nets will be shredded. They also have trouble disposing of the jellyfish. With little options available, they hold the jellyfish in the nets until they die. The nets become tombs for jellyfish. With a body composition that is 90% water, dead jellyfish decompose in about 10 days in the nets. But researchers recently discovered that the dying jellyfish spawn eggs prematurely. To leave as many offspring before they die, they spawn all at once. Cone-shaped polyps appear when eggs are fertilized by sperm. The white fungus-like specks in the ocean are actually jellyfish polyps. Jellyfish reproduce at a remarkable rate. One polyp can spread like a virus and spawn other polyps. Each polyp then releases several baby jellyfish. Thus, one polyp can produce hundreds of baby jellyfish. As soon as the jellyfish is spawned, it will start feeding on zooplankton. They are highly adaptable and mature into adults in about a month. These swarms of jellyfish are thrown back into the ocean. Unless the jellyfish are disposed of when caught, they will continue to wreak havoc. With jellyfish plentiful in the ocean, a crab catches one for food. It will feast on jellyfish all summer. This jellyfish is entangled on the sharp spines of a sea urchin. With its tentacles caught on the spiny sea urchin, it's unable to free itself. Jellyfish populations have increased due to pollution and rising ocean temperatures due to global warming. Swept by the sea currents, a tropical jellyfish appears. This highly venomous jellyfish was non-existent in the waters surrounding Korea until recently. They silently creep into Korea's shallow waters. Tropical jellyfish are now common sights in Korea's waters. Experts predict that about 124 jellyfish species not found in Korea will begin appearing in the nation's waters. Among them, 100 are venomous. Currently, the Nomuras jellyfish is the largest threat. Its venom is highly poisonous and emits venom when it detects any nearby movement. It is highly dangerous to humans. In July and August, jellyfish terrorize beaches. When a jellyfish stings a person, their skin will start swelling immediately and the pain will be excruciating. A serious jellyfish sting can kill a human being. Even after treatment, the scars remain for life. Other strange occurrences are found on the sea floor. Swarms of sand dollars, which feed on organic material, appeared in the surrounding ocean. When they die, they turn white and display a lotus pattern. The sudden appearance of this sand dollar swarm is an indication that the ocean environment has changed. More types of fish inhabit the nation's waters. Mink whales fetch high prices at the market, and more of them are caught in nets across the nation. Having baleen plates for filtering zooplankton instead of teeth, mink whales are sighted more frequently off the coast of Korea, probably due to the rise of the plankton population. There are also other rare specimens appearing. This whale shark was caught near Jumunjin Port. Adult whale sharks can be 10 meters long, and they usually inhabit tropical waters where they feed on plankton. The sightings of the whale sharks is a sign that the sea is changing. If global warming continues unabated, the fish stock around Korea will undergo a radical change. Near the end of summer, fanworms get ready to spawn. It spreads its tentacles to scatter its egg. The spawning season is a celebration of life for these fanworms. In the mating season, this pair of crabs are getting intimate. With its body covering the female, the male crab begins its courting ritual. An octopus is caught inside a fish trap that was laid out in the middle of the sea. It looks for an opening in vain. Once a creature enters a fish trap, it is nearly impossible to escape. We find the body of this lifeless crab in the trap. But the octopus extricates itself from the net. Through a tiny opening, it magically escapes. It was on the verge of meeting an untimely death, but the octopus is now free. Fully grown, this numerous jellyfish roams the sea. It is as large as a beach umbrella and weighs more than 100 kilograms. The jellyfish grew at a stunning rate in just three months. There seems to be nothing that can stop it. But it faces an obstacle. It's a fish net. But when a swarm of huge jellyfish appears together, they can do enormous damage. Damaged nets will lead to heavy losses. Touching a jellyfish is dangerous, and it's futile to extract one jellyfish when there are so many. This Nomura's jellyfish is edible but tasteless. Chinese buyers come to buy these jellyfish, but fishermen have given up on hauling them in because of their weight. Not too long ago, traditional markets did brisk business in selling jellyfish. But now they are shunned. Jellyfish contain peptide, which can cure high blood pressure. If they're marketed well, these irritating creatures can be turned into a popular health food. Only a few fish species eat jellyfish. Striped beak perch and thread sail filefish eat jellyfish. But they only attack dead jellyfish and never dare to eat a live one. There are no natural predators of jellyfish in Korea's waters. What is despairing is that there are no measures that can repel the swarms of jellyfish. When jellyfish get caught in small fish nets, they are hurting the livelihoods of fishermen. These creatures dash the hopes for a big catch. Are the fishermen aware of the situation down below the ocean? These men go out to sea at night. Their nets are full of jellyfish. They open up the net to let the jellyfish out into the sea. But they've been dealing with this for quite some time. Their next net also turns up more jellyfish. The captain has to cover the fuel costs and pay his men, so they start separating the jellyfish from the fish. They look on with anger and bitterness. Jellyfish appear at night or during the day. A net that they haul in during the day is flooded with jellyfish. They dispose of the jellyfish by throwing them overboard. The jellyfish that they throw back into the sea clogs up another net. This in turn leads to the entanglement of different nets. Having little space to move in the tangled nets, the fish die quickly. They should be hauling in plenty of fish during this time of the year. It is harder to make a decent living. Most of the fish in the nets are already dead. Even the ones that are alive have been stung by jellyfish and will die soon. The live fish can't be sold at the market after being stung. They shovel the fish into the sea after working hard all day. It's useless to bring in a catch that will have no buyers. The domestic fishing industry has suffered about 300 million dollars in damages due to jellyfish. More fishing boats are moored at the ports these days. It's a dire situation. This is a case where humans are helpless against the forces of nature. Here on the coast of Taeyang County in September. The season for catching Japanese Spanish mackerel should be over by this time of the year, but the warm ocean temperatures have prolonged their stay. After suffering a drought, the fish are forced to migrate to the sea. Suffering losses from jellyfish swarms, this is a bright spot in the fishing industry. Mackerel is caught through real fishing methods. They use plastic bait, which does minimal damage to the environment. They attach several fishing lines to a bamboo rod and reel it in when the rubber bands stretch to a certain point. Rising sea temperatures caused by global warming is changing the fishing season. It's chillier now in November. Rows of squid are dried under the sun. In the winter season, there should hardly be any jellyfish in the ocean. The jellyfish we spotted move sluggishly. The temperature is 15 degrees Celsius underwater. It has dropped 8 degrees compared to the summer. Nomura's jellyfish become less active in temperatures below 18 degrees Celsius. With death near, the jellyfish lies on the ground and lets the sea current toss it around. On the threshold of death, they have lost all their vitality. After causing enormous damage to the fishing industry, the jellyfish lie lifeless on the seafloor. But these dying jellyfish still inflict one last blow to the ocean environment. They suck in oxygen as they rot. Furthermore, they emit ammonia gases. These two after-effects from their deaths create an uninhabitable environment. It's November off the coast of Sokcho. The fishermen sail off to cast their nets again. Fortunately, they find no jellyfish in the nets. It's a big catch that they've been waiting for all year. The fish flail around. This is how things used to be. However, if jellyfish stay for extended periods in the nation's waters as global warming cause ocean temperatures to rise further, a bountiful catch can become less frequent in the future. In the summer season, jellyfish decimated fish populations. Fishermen were unable to fend off swarms of this silent, slow-moving menace. Global warming, overfishing, and pollution have brought these swarms of jellyfish to Korea's waters. These jellyfish swarms have ravaged the fishing industry. However, they could also be a warning to us that we need to change. What kind of damage will jellyfish inflict on Korea next summer? The ocean needs our help.