Sea Monsters: Trouble With Jellies

Clicking around the Cracked website, as I sometimes do when life hands me lemons and I need a really good laugh, I found this article: 6 Animals Humanity Actually Made Way Scarier. Questionable grammar not withstanding, most of the logic in the article is pretty sound. Cougars are really losing habitat, making them more likely to have dangerous encounters with humans. Wolves really did crossbreed with coyotes in the northeastern U.S., creating a powerful predator that is blithely unafraid of human populations. I’m not going to argue with that. But the first animal on the list needs to be looked at, and its actually threat analyzed, a little more closely.


The piece is particularly concerned with giant Nomura jellyfish, found largely in the tropical Pacific, and box jellies which are common in the waters of Australia. Both creatures, which are nasty for very different reasons, have seen a decided upswing in population since the beginning of the 21st century. As the article notes there are three pretty clear reasons for this explosion.

The number one reason is ocean warming. Say what you want about climate change, the warming of ocean waters around the globe is a documented fact that has been occurring without cessation since at least the last decade of the 20th century. For reasons we don’t quite understand, jellyfish in general respond to a warmer environment by breeding more and swimming closer to shore. Other factors are pollution, particularly by agricultural fertilizers which encourage growth in plankton, and overfishing of certain jellyfish predators. All bad news on the face of it and the cause of everything from enormous “jellyfish blooms” off the coasts of places as diverse as Australia and Ireland to the complete shutdown of fishing operations in Japan and desalinization plants on the Black Sea. Even the Bering Sea – yeah that “vast Bering Sea” – has seen large trawling nets break due to huge swarms of heavy jellyfish attacking the catch within.

So is it really that bad? Are we doomed to be stung mercilessly by veritable herds of virtually invisible box jellies? Or have our precious Omega 3 fatty acids ripped from our mouths by 450 pound Nomura monsters? In a word, no.

Even though some jellyfish predators have been overfished, others are either doing just fine or coming back strong. Those delightful Opilio and King crabs that you see being hauled up in traps on “Deadliest Catch” are in great shape numbers-wise due to smart conservation and they will happily chow on just about any jellyfish that gets within range. Likewise Blue Swimmer crabs delight in feasting on box jellies around Australia and particularly the Philippines where the highest percentage of deaths by jellyfish sting are reported yearly. Another common predator of the box jellies was once endanger but is now, thanks in part to the large numbers of one of its favorite snacks, growing in population: the sea turtle. Sea turtles, legendarily a delicacy to seaman around the world, are completely immune to the sting of even the most venomous box jellies, Chironex fleckeri and Chironex yamaguchii. Even these guys are no match for the hungry terrapins.

So while cyclical “blooms” of jellyfish will doubtless continue to be a problem worldwide, it may be a little early to panic. Simply minding the good advice on the Australian sign above is probably your best bet, and just in case, put some vinegar in your beach bag. And don’t forget to say thank you next time you run into a crab or a sea turtle.

Header: Sign at Cape Tribulation, Australia via Wikimedia Commons