I reserved Eating Jellyfish as a domain name about 6 years ago, when the prospect of eating jellyfish seemed an absurd outcome of overfishing, coastal development and pollution now clearly associated with the occurrence of schools or blooms of jellyfish. Jellyfish as the top predators in coastal ecosystems are now even more common. As we are forced to adapt, the idea of eating jellyfish is no longer as absurd as it was. And yes, of course, some cultures have a long history of eating certain species of jellyfish: it is just a very alien idea to the rest of us.
Recent reports of unexpected and large jellyfish blooms have come from most parts of the world – from the seas of Japan, China and Europe especially, but also from West Florida and the Gulf of Maine. What actually causes the blooms is not certain, for until recently nobody was really interested enough to try to find out.
But what we know is this: jellyfish blooms are associated with coasts of dense human populations where overfishing, eutrophication, habitat modification, invasive species, and a warming climate may all be involved. One of the most famous and clearest cases occurred in the Black Sea, where overfishing, warmer water, and nutrient enrichment from the Danube made for perfect conditions for a succession of jellyfish to explode in number.
Probably the other most famous blooms involve the giant Nomura’s Jellyfish in the Sea of Japan, each a monster, hard to harvest even if you wanted to, and immensely damaging to fisheries and fishing nets.
The most prolific and widespread is Aurelia aurita, the moon jellyfish, for it is globally distributed, and capable of explosive growth into very large populations. I have fond memories from when I was kid on the coast of Maine heaving dead washed up moon jellyfish at my sisters.
Why are jellyfish so successful in degraded conditions? In a health ecosystem they compete with fish for access to food – mainly zooplankton. Where overfishing has removed the competing fish, they have few limits to growth. In eutrophic conditions, for instance around the mouths of major rivers carrying high loads of P and N, they also tolerating the lower levels of dissolved oxygen that fish avoid: where coastal nutrients increase, so to do jellyfish. The result is a trophic cascade, a regime change, an ecosystem that is free of fish predators, dominated by jellyfish, and of very little value or interest to humans.
What’s ahead, then? All of the stresses – overfishing, eutrophication, warming waters, habitat modification, human population densities are all likely to keep increasing along our coastlines.
We can do a couple of things about this. Of course trying to recover such stressed ecosystems, restoring fish as top predators, is the best, but not most likely outcome. Instead, we can also learn which species of jellyfish are actually possible to harvest and eat (some taste horrible). There are also likely to be some yet-to-be discovered medical uses of some species. And perhaps jellyfish have some potential as supplements to animal feeds.
We also need biologists who can help integrate knowledge of jellyfish ecology with that of the whole ecosystem, making jellyfish part of what fisheries scientists must consider in their attempts to manage both fisheries and ecosystems.
Jellyfish as components of fisheries, and jellyfish as components of our own diets, are facts of life in this critical century.
We just have to suck it up. They’re mostly water anyway.