In 2007, a 'bloom' of the giant jellyfish Nemopilema nomurai drove Japanese fishermen to distraction. Caught in trawls, the monster jellies (some up to 2m across and 200 kg in weight) caused problems by stinging fish, breaking nets and threatening to capsize vessels*. The fishermen had to fend them off with bamboo poles. Not only were the fish catches buggered but Nemopilema was not a good replacement for the lost harvest. The texture's not quite right, apparently. Not crunchy enough.
But whereas the jellyfish have been rejected at the ocean surface, a whole bunch of creatures on the ocean floor have been chowing down on the carcasses. A study of 138 dead jellies in the Sea of Japan revealed their importance as a source of organic matter in a habitat where the locals rely on bounty from above.
Nemopilema was popular with four species of scavengers: Pandalopsis japonica (shrimp), Chionoecetes opilio (snow crab), Buccinum striatissimum (ivory whelk) and Ophiura sarsii (brittle star). How popular? Ten kilogram chunks o' jelly were reduced by 30 – 50% in less than a day. And the fishermen top side say that they're not crunchy enough. It just doesn't make sense.
Reference
Yamamoto, J. et al. (2008). Transportation of organic matter to the sea floor by carrion falls of the giant jellyfish Nemopilema nomurai in the Sea of Japan. Marine Biology 153: 311 – 317.
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* By their weight in the net, rather than any co-ordinated and malicious intent. But I'd pay good money to see a film about a bunch of vigilante jellyfish roaming the ocean with revenge on their minds.
