I should preface this with the fact that my experience with jelly fish is limited. To me, they’re just an occasional nuisance that looks cool at the aquarium. I’ve only been stung once, but I did have to wear a fashionable blue unitard to go snorkeling on the Great Barrier Reef and avoid the seasonal danger of getting stung by a tiny, (sometimes) lethal box jellyfish.
Jellyfish have been around for millions of years, and jellyfish blooms, in Australia and elsewhere, are just another facet of a healthy ocean environment. But, blooms are becoming more and more common, and spawning the In the Sea of Japan, a now almost yearly swarm of the gigantic Nomura’s jellyfish (Nemopilema nomurai) famously capsized a boat. Large blooms disrupt fishing industries and even shutdown nuclear power plants.
Jelly fish blooms are cyclic and seasonal — lots of factors come into play like sun exposure, temperature, nutrient levels, changes in ocean currents, and the balance between predators and prey in the ecosystem. Some scientists think human influence might be the underlying issue. Agricultural runoff can add nutrients to the system, providing more food to the zooplankton that jellies eat.
Fishing can also take competitors — small pelagic fish (fish that live in the water column, near the ocean surface) such as sardines, herrings, and anchovies — out of the ecological equation. Jellies also feed on these fishes’ eggs and larva, and sans regulation, their populations can easily explode and invade new territories. Thus, over-fishing is another suspect that some scientists and conservationists point to, and a recent paper in the Bulletin of Marine Science adds evidence to the pile.
Researchers at France’s Institut de Recherche pour le Développement (IRD) present two contrasting case studies in the Benguela ocean current, which flows north along the southeastern coast of Africa. In the first, just off the coast of Namibia in an area with lax fishing regulations, pelagic fish populations barely have time to recover before fishing stars up again, and jellies are already colonizing the area. If the current trajectory plays out, sardines and the like might one day be absent from the local food chain, with negative implications for the ecosystems other inhabitants. On the other hand, the small fish still dominate the second ecosystem, off the coast of South Africa where strict fishing regulations have been in place for nearly half a century.
These scientists aren’t the first to point to over-fishing as the problem. A 2009 review paper published in Trends in Ecology and Evolution pin-pointed over-fishing, in addition to the effects of climate change and excess nutrients from fertilizers and sewage run-off, as a compelling culprit for jellyfish population growth.
“Mounting evidence suggests that open-ocean ecosystems can flip from being dominated by fish, to being dominated by jellyfish,” Anthony Richardson, a marine ecologist and a co-author, said in a statement at the time. “This would have lasting, ecological, economic, and social consequences. We need to start managing the marine environment in a holistic and precautionary way to prevent more examples of what could be termed a ‘jellyfish joyride’.”
Other researchers suggest that jellyfish are doing the same thing in Antarctica, and out-compete local penguins species.
Though some scientists think global jellyfish populations are booming, others aren’t convinced. The data is iffy (from anecdotes and case studies), and historic jelly population data is even worse. These pesky blobs are ridiculously hard to study, especially when they rival sumo wrestlers in weight. However, one group of marine biologists is tackling the daunting task of crunching jellyfish numbers. Their results published earlier this year in PNAS, say that the evidence for a jellyfish population explosion just isn’t there (…yet). It turns out that jelly fish populations oscillate over a natural 20ish year period. They also detected a small linear uptick since the 1970s, but only further monitoring will tell if that trend is a serious problem or a minor blip.
So, if we are indeed on a ‘jellyfish joyride’, how do we get off? One solution or consequence (depending on how you look at it): eat the jellies. It fact, jellyfish ending up on dinner plates seems to be the go-to example of the hardships we’ll face with over-fishing and other global food-related crisis.
Upon reading this, I could not help, but google, “jellyfish edible”. It turns out that some species are harvested for food. They produce tentacle toxins that are not harmful to humans and/or their bodies are more rigid. Rhopilema esculentum is popular in China, while Cannonball jellies (Stomolophus meleagris) off the US east coast are growing in popularity, as well.
In fact, jellyfish has been a staple of Chinese cuisine (read not Panda Express) for centuries. “Jellyfish masters” (I kid you not, it’s an actual job title) soak jellyfish strips in a salty mix, dry them, and ship them off to restaurants, where chefs rehydrate the strips and serve them raw or cooked. Smithsonian describes “cold shredded jellyfish” purchased at Jackey Cafe in DC’s Chinatown as “wetly crunchy” in a seaweed salad sort of way. Yum?