Japan Awaits This Year's Giant Jellyfish Invasion

Nomura's jellyfish can grow to 6 feet in diameter and weigh more than 450 pounds. Scientists believe they originate in the Yellow Sea and in other Chinese waters.

The danger to fishermen isn't as much because of the toxicity of the Nomura's jellyfish stings, as Wikipedia states:

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 main problem of the Nomura's jellyfish comes when they get trapped in fishermen's nets, tearing holes and ruining catches. This could severely impact the Japanese fishing industry.

Scientists are unsure why Nomura's jellyfish are invading the Sea of Japan in recent years. The spectre of global warming has raised its head, however, theories have been posited that overfishing, pollution or rising ocean temperatures may have depleted the fish that would prey on Nomura's jellyfish in the polyp stage.