Nomura's Jellyfish are gigantic creatures (they can grow up to 2 meters in diameter and weigh as much as to 220 kilograms) which have plagued the seas of Japan from 2005 up to present. These giant jellyfish normally reside in the Yellow and East China Seas but warm ocean currents seem to be bringing these monsters to Japan. 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. 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. Watch them here.
The main problem with this invasion is the devastation it wreaks on commercial fishing. They decimate fish populations and it only takes a couple of these sumo wrestler sized animals to destroy a harvest net. The risk of a fishing boat capsizing due to having a number of these creatures caught in its nets is a real and present danger. In addition fishermen suffer by being stung when trying to remove these jellyfish from their nets.
Japan has tried to kill the creatures before they reach Japan, however the Nomura’s Jellyfish has an unusual survival mechanism in that when it is attacked or killed it releases millions of sperm and eggs which then attach to rock and coral formations. When they mature they release from the rock, millions at a time, and become jellyfish. Japan has also tried to use the surplus they have of this creature, trying to create a market for in the way of foods, and cosmetic products.
For possible causes (overfishing, pollution and global warming) read the previous post: jelly invasion. In line with the pollution arguments mentioned there, the building of the Three Gorges Dam on the Yangtze River in China, hence releasing excess nitrogen and phosphorus, indeed seem to have created a friendly environment for breeding.
In any event, should the problem these monsters create not be dealt with in an efficient manner, what is sure is that harvests of salmon, anchovies, and tuna will suffer.
source 1, source 2, source 3
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