Exactly. If there are really tons of these things, why don't we find a use for them (cold as it might seem)?

Food, (Animal food, human food. What can they be processed into, do they contain any useful nutrients or protein, if so, blend them up, add something to incapacitate the stingers, add flavour and et voilà: Soylent jellyfish!), Fuel, Plastic, Medicine...Glue?

I mean it doesn't solve the underlying problems, but they might be a relatively unexplored resource.

I agree: industrial uses seem the most promising. It seems unlikely we'll convince half the world to start loving jellyfish. But it seems plausible we can convert jellyfish into useful substances or derivatives.

Even still, the article addresses deeper problems. Killing back the jellyfish won't stop the conditions that we are causing in the oceans -- conditions that are extremely suitable to jellyfish, and seem suitable to little else. Acidification, warming, pollution, etc.

One little-heralded fact, for instance, is that we're coming dangerously close to driving sharks to extinction in many of the world's ecosystems. An ocean with fewer sharks in it? It's tough to find people who will shed a tear. But killing off the keystone predators in an ecosystem throws the whole thing into chaos -- and as it turns out, paradoxically, killing off sharks is a fantastic way to kill off most of the fish sharks feed on.

The point of my digression is that doing something about the "jellyfish menace" is probably necessary at this point. But it's not sufficient. It's a band-aid on a bullet wound.

Fertilizer would appear to be the logical solution. Compost a giant pile of them for six months and apply to fields.

Also let them rot into methane and burn the methane (probably combined with option 1 above).

You can't make a decent compost with pure 100% jellyfish, but added to another waste deficient in different nutrients, it might add up.

The article didn't discuss weaponization of jellyfish, which is the most likely funding source. Shutting down a regions desal and power plants by releasing a short lived poorly adapted jelly is a lot less visually impressive than a bombing campaign, but probably a lot cheaper. Or rather than the animals themselves, dump food for them, perhaps.

This would make for an interesting experiment. Anaerobic digesters would presumably make short work of any toxin proteins, and you could probably get a fairly high jellyfish to "other" feedstocks [ratio] while retaining a commercially viable fertilizer (plus plenty of usable methane) as end products.

That said, I doubt that the cost to harvest and transport would be competitive with more conventional feedstocks such as slaughterhouse leavings, crop wastes / stalks, and plain old manure.

Food for thought, anyway. Floating digester platforms, maybe?

[edit: added missing word 'ratio']

The issue with this?

1. It doesn't solve the underlying problem.

2. It guarantees that the underlying problem will never be solved because there is now an industry dependent on the problem existing. They will fight tooth-and-nail to keep the problem in existence.

But maybe that would buy enough time for other parts of the equation to shift... It seems to me that we humans tend to change things up faster than our environments can keep up, but our environments do eventually change.

Maybe if we are part of a process that lowers the number of Jellyfish, another part of the equation will surface to help: Natural predator, loss of needed food/fuel for Jellyfish, etc.

We are always having to adapt to changing circumstances, this may help solve the immediate problem and may give us time to face the changing environment of the future.

I do not think humans can ever do anything that would be considered perfect on all fronts...

figure out how to use them for energy production ;)

Convince people that it is even better for "potency" than shark fin or black rhino horn.

Make it the next Japanese delicacy. Surprised it isn't already.

I guessing the net energy return from fishing jellies is negative. If they were such an awesome source of energy, we wouldn't have the current problem (lots of things eat poisonous things).