echizen kurage (エチゼンクラゲ)

Growing up to 2 m (6 ft 7 feet) in diameter and weighing up to 200kg (440 lb), Nomura's Jellyfish reside primarily in the waters between China and Japan, primarily centralized in the Yellow Sea and East China Sea where they spawn.

While stings of this large jellyfish are painful, they are not usually toxic enough to cause serious harm in humans. However, the jellyfish's sting has been reported as fatal in some cases by causing a build-up of fluid in the lungs. As a precaution, fisherman encountering these jellyfish wear eye protection and protective clothes. To date there have only been eight reported deaths from the Nomura's sting.

The problem with combating the jellyfish is that when they are under attack or killed, they release billions of sperm or eggs which connect in the water and attach to rocks or coral formations. when the conditions are favorable, the creatures detach from their home millions at a time and grow into more jellyfish.

In an attempt to utilize the jellyfish in a productive manner, coastal communities in Japan are doing their best to promote jellyfish as a novelty food, sold dried and salted; students in Obama, Fukui (Japan) have managed to turn them into tofu, and jellyfish collagen is also reported to be beneficial to the skin.

http://en.wikipedia.org/wiki/Nomura's_jellyfish