June 8, 2009 — Giant jellyfish like this one are taking over parts of the world’s oceans as overfishing and other human activities open windows of opportunity for them to prosper, say researchers. In this photo, a diver is attaching a sensor to track a monster Echizen jellyfish, which has a body almost 5 feet across, off the coast of northern Japan. Jellyfish are normally kept in check by fish, which eat small jellyfish and compete for jellyfish food such as zooplankton, researchers said. But, with overfishing, jellyfish numbers are increasing.
These huge creatures can burst through fishing nets, as well as destroy local fisheries with their taste for fish eggs and larvae. Anthony Richardson of CSIRO Marine ; Atmospheric Research and colleagues reported their findings in the journal Trends in Ecology and Evolution to coincide with World Oceans Day. They say climate change could also cause jellyfish populations to grow. The team believes that for the first time, water conditions could lead to what they call a “jellyfish stable state,” in which jellyfish rule the oceans.
The combination of overfishing and high levels of nutrients in the water has been linked to jellyfish blooms. Nitrogen and phosphorous in run-off cause red phytoplankton blooms, which create low-oxygen dead zones where jellyfish survive, but fish can’t, researchers said. “(There is) a jellyfish called Nomura, which is the biggest jellyfish in the world. It can weigh 200 kilograms (440 pounds), as big as a sumo wrestler and is 2 meters (6. 5 feet) in diameter,” Richardson said. Richardson said jellyfish numbers are increasing in Southeast Asia, the Black Sea, the Gulf of Mexico and the North Sea.
Photo credit: Yomiuri Shibun/AFP/Getty Images Giant jellyfish are flooding into the Sea of Japan. The translucent creatures can grow as large as 6 feet in diameter and weigh 450 lbs. Over the last 5 years, millions have migrated from the coast of China into Japanese waters. Scientists believe they’re floating in on ocean currents warmed by global climate change. The jellyfish are so heavy they rip the nets of Japanese fishermen and their venom poisons the rest of the catch. The country’s fishing industry has been devastated.
But a Japanese entrepreneur has decided to make lemonade out of these marine lemons. Kaneo Fukuda calls himself “Jellyfish Fukuda” and he claims to have developed more than 20 products made out of the jellyfish. He’s marketing everything from makeup to mixed drinks. Anyone for a Jellyfish Sour? Are aliens attacking the Sea of Japan? Not exactly. But these gigantic blobs are unwelcome visitors from another place. Called Nomura’s jellyfish, the wiggly, pinkish giants can weigh up to 450 pounds (204 kilograms)—as heavy as a male lion—and they’re swarming by the millions.
The supersize sea creatures—normally found off the coasts of China and North and South Korea—occasionally drift east into the Sea of Japan to feed on tiny organisms called plankton. But now one hundred times the usual number of jellyfish are invading Japanese waters. And local fishermen are feeling as if they are under siege. The fishermen’s nets are getting weighted down, or even broken, by hundreds of Nomura’s. The jellies crush, slime, and poison valuable fish in the nets, such as the tuna and salmon that the fishermen rely on to make a living. No one knows for sure what’s causing this jellyfish traffic jam.
It’s possible that oceans heated by global warming are creating the perfect jellyfish breeding ground. Another theory is that overfishing has decreased the numbers of some fish, which may allow the jellies to chow down without competition for food. For now, all the fishermen can do is design special nets to try to keep the jellies out. Some of them hope to turn the catastrophe into cash by selling jellyfish snacks. Peanut butter and jellyfish, anyone? Fast Facts * Baby Nomura’s jellyfish change from the size of a grain of rice to the size of a washing machine in six months or less. * Jellyfish are 95% water. Jellyfish aren’t actually fish, they’re invertebrates—animals without backbones. * OKI, Japan — Fisherman Ryoichi Yoshida pulled in his nets before dawn one morning, hoping for lots of yellowtail and mackerel. But the fish were overwhelmed by a heaving mass of living pink slime. * The creatures, called Nomura jellyfish, can measure six feet across and weigh up to about 450 pounds. They have been drifting en masse to places like Oki, a small island 40 miles off the coast, bobbing beneath the surface of the water like pink mines. They rip holes in fishermen’s nets, and they poison fish. “Normally, we just bring up the nets and it takes about an hour,” said the weather-beaten Mr. Yoshida, 61 years old, after his crew had cleared the jellyfish out of the nets using long poles and hooks. “Now it takes two or three hours. And some of the fish escape. ” * Until 2002, these giant creatures were seen only occasionally in Japanese waters. But for the past five years, they have been swarming every year into the Sea of Japan, the water that separates Japan from mainland Asia. During the biggest invasion so far, in 2005, an estimated 500 million jellyfish — not yet mature — drifted in each day. It’s hard to calculate financial damage to fishermen, but the Japanese government last year counted about 50,000 incidents of jellyfish trouble. Fish poisoned by jellyfish tentacles die with their mouths agape. That mars their appearance and reduces their value by as much as 20%. “When their mouths are wide open, it means they’ve died going, ‘I’m in pain! I’m in pain! ‘ ” explains Mr. Yoshida. * Scientists have various ideas about what causes the outbreak. One has devised a computer model of ocean currents that suggests the jellyfish are breeding off the Chinese coast near the mouth of the Yangtze River.
One theory is that pollution, perhaps linked to industrialization in China, is helping create more algae in the sea. The algae are food for plankton, which is food for jellyfish. * Three Gorges Dam * Then, too, there is speculation about a link to the Three Gorges Dam, the world’s largest hydroelectric-power project under construction in the Yangtze, which could be changing water flows to the sea. A dam in a section of the Danube that runs between Serbia and Romania completed in 1972 changed the river flow, after which the jellyfish population of the Black Sea exploded. Chinese officials and scientists deny that Chinese pollution has caused the outbreaks. * “No research evidence in China supports a connection between pollution and jellyfish,” says Li Qi, a dean of the Ocean University of China. “Floating jellyfish are mostly in the Sea of Japan…. That’s Japan and Korea’s problem. ” * Eager for a solution, slasher squads of fishermen went out last year armed with barbed poles to attack jellyfish that were jamming up nets. If the jellyfish are cut into three or more bits, they usually die and get eaten by other sea creatures. * Fishermen have also taken a trawl net and added a wire grill like a large potato masher at the trailing end: When the net is pulled through a swarm of jellyfish, they float through and are sliced up. * The Japanese government is doing what it can. It tracks the progress of jellyfish as they swarm through the Sea of Japan, urging trawlers to steer clear of them. The Japanese harvest some jellyfish to eat. Jellyfish can be boiled and added to salads — though smaller varieties are said to be more tender and tasty.
Trying to win converts, the fisheries ministry has drawn up a manual with tips on cooking with giant jellyfish. Menus include jellyfish-flavored biscuits, jellyfish soaked in rum and a dessert of jellyfish chunks in coconut milk. * Jellyfish Ice Cream * One coastal firm, Tango Jersey Dairy, has for the past three years produced 2,000 or 3,000 cartons of vanilla-and-jellyfish ice cream. The jellyfish is soaked overnight in milk to reduce its smell, and is then diced. Fumiko Hirabayashi, a director of the dairy, says the jelly cubes are slightly chewy.
Jellyfish is also getting publicity in women’s magazines because it contains collagen, a protein used in cosmetics. * “We think it’s important to use local ingredients,” says Mrs. Hirabayashi. “And this has now become a local ingredient. ” * Despite the damage they cause, jellyfish are actually delicate creatures. The Marine World aquarium in Fukuoka, west Japan, displayed two giant Nomuras in 2004. Despite the care taken with the cranes used to put them into tanks, the jellyfish quickly took sick, and they died in just a couple of weeks.
Echizen Matsushima Aquarium in Fukui, one of the costal areas most affected by the influx, has been displaying the jellyfish since 2005. But they soon die, too, and must be replenished. * One fear among scientists is that the creatures are multiplying in a “jellyfish spiral. ” Shinichi Uye, a leading jellyfish researcher at Hiroshima University in western Japan, thinks overfishing off China has led to fewer plankton-eating fish, leaving more plankton for the jellyfish to suck up. This growing army of jellyfish then also eats fish eggs, resulting in even fewer fish. *
Whatever the details, says Prof. Uye, the problem seems to be industrial development. “It’s like a harmless living thing has been angered,” he says. “The reason for its anger might lie with human activity. ” * * Trying to understand why the jellyfish have started appearing in such numbers, marine biologist Kohzoh Ohtsu studies their reproductive cycle on another part of Oki. One afternoon he and a colleague — dressed in rubber clothing to protect against the poison — cut lumps of tentacle from a 200-pound jellyfish with a knife to make it light enough to bring aboard. One cause of the mass invasions, he says, “could be rising sea temperatures” making it easier for the jellyfish to breed and feed near China. * Though he doesn’t know details of the sea temperatures there, the peak water temperature in the Sea of Japan has been four or five degrees Fahrenheit higher than normal in a couple of recent years, indicating warmer seas in the region. One fear is that higher temperatures or other environmental changes might one day even allow the giant jellyfish to breed around Japan, adding further to their numbers. * Dedicated Research * Prof.
Ohtsu has dedicated his research to jellyfish since 2003, after they became a national problem, and his quest to unravel the mystery continues year-round. He lives at his marine research center in an isolated part of this small island, and is alone there most of the year — except for a laboratory full of jellyfish at different stages of development. He travels to the Japanese mainland about twice a month, but the trips have to be kept short. * “I have living things here, so I have to keep an eye on them,” he says. “If you leave them for three or four days, they don’t look too good. They are very delicate. * Japanese researchers monitoring the activity of giant jellyfish in Chinese waters are warning of a potentially historic and catastrophic invasion this year. * Marine surveys conducted in late June have revealed alarming numbers of Nomura’s jellyfish — massive creatures that grow up to 2 meters (6 ft 7 in) in diameter and weigh as much as to 220 kilograms (about 450 lbs) — lurking in the Yellow Sea and East China Sea. The researchers warn that ocean currents may bring swarms of the monster jellies to Japan, which has been plagued by similar invasions in recent years. * Nomura’s jellyfish, 2007 (Photo: Sankei) Based on what they have seen so far, the researchers warn this year’s onslaught of Nomura’s jellyfish (Nemopilema nomurai, or Echizen kurage in Japanese) could deliver a massive blow to Japan’s fishing industry, rivaling even the devastating 2005 deluge that caused tens of billions of yen (hundreds of millions of dollars) in damage nationwide. * The surveys are being conducted by a team led by Shinichi Ue, a professor of biological oceanography at Hiroshima University who also chairs a government research committee tasked with developing technology to predict and control jellyfish explosions.
Ue has been monitoring the population density of Nomura’s jellyfish in the southern Yellow Sea and northern East China Sea since 2006. * Between June 20 and 24, 2009, Ue’s team observed numerous specimens with umbrellas measuring 10 to 50 centimeters across, and they calculated an average distribution of 2. 14 jellyfish per 100 square meters. This figure is more than 200 times higher than the 0. 01 jellyfish per 100 square meters observed in the same region in 2008. It is also nearly triple the 0. 7 jellyfish per 100 square meters observed in 2007, when the fishing industry in the Sea of Japan suffered widespread damage. * Nomura’s jellyfish, 2007 (Photo: Sankei) * To make matters worse, this year’s swarms appear to be taking a more direct and southerly route to Japan, unlike in 2007 when the jellyfish appeared to take a more northerly route, approaching the Sea of Japan coast from the direction of Korea. According to the researchers, the ocean currents could bring unprecedented numbers of Nomura’s jellyfish to Japan’s Pacific coast, which typically sees far fewer of the monster blobs than the Sea of Japan coast. Nomura’s jellyfish typically bloom in Chinese waters in spring, and they mature into adults as ocean currents slowly carry them north. By July, when the first swarms reach Tsushima (just north of the southern island of Kyushu), many jellyfish are as large as sumo wrestlers. At this size, it only takes about 5 or 10 of them to destroy a commercial fishing net. * In addition to damaging nets, the giant jellyfish are blamed for killing other fish with their venom, lowering the quality and uantity of catches, increasing the risk of capsizing trawlers, and stinging fishermen. * In 2005, the fishing industry reported over 100,000 cases of jellyfish-related damage nationwide. At the peak of the invasion that year, an estimated 300 to 500 million monster jellyfish passed through the Tsushima Strait into the Sea of Japan each day. Kingdom:| Animalia| Phylum:| Cnidaria| Class:| Scyphozoa| Order:| Rhizostomae| Family:| Stomolophidae| Genus:| Nemopilema| Species:| N. nomurai| Binomial name| Nemopilema nomurai (Kishinouye, 1922)|