In 2005, and again last year, Japanese fishermen battled swarms of giant Nomura jellyfish, each measuring six feet across and weighing 200kg.

2005年，以及去年，日本渔民同成群的“越前水母”展开斗争，每只水母直径1.8米，重200公斤。

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But recently fishermen off the coast of Japan have as often been pulling in jellyfish: the giant echizen kurage, Nomura's jellyfish, which can be over a metre across and weigh more than 150 kilos (330lbs).

ECONOMIST: A netful of trouble for Japanese fishermen

It's not clear why waves of Nomura's jellyfish have made it to the Sea of Japan in recent years.

CNN: Japanese fishermen brace for giant jellyfish

Some have speculated that overfishing, pollution or rising ocean temperatures may have depleted the kinds of fish that prey on Nomura's jellyfish in the polyp stage.

CNN: Japanese fishermen brace for giant jellyfish