Invasion of the Ecosystem: Alien Species Scarier than Fiction
Nomura's jellyfish Japan
They look more like something out of Doctor Who than the jellyfish seen in European waters. But since last year Japan's coastline was invaded by the massive sea creatures which can grow up to 6.5 feet (2 metres) wide and weigh up to 450lb (220kg). The creatures, which are normally found further south in the waters off China and Korea, have caused problems with local fishermen by clogging their nets and poisoning their catches. One theory is that the plague has been caused by heavy rains which swept the giants from China's Yangtze river delta to Japan, but others believe that, because of global warming, seas have been warmed and are better suited for breeding jellyfish. In addition to this, scientists blame over-fishing of natural predators that feed on jellyfish and pollution along the continent's coasts. Human injury is rare but a few unlucky swimmers have been killed.