Watery Snacks

April 28, 2019
By Damond Benningfield

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Jellyfish make up a surprisingly large portion of many animals' diets. Photo Credit: NOAA

Jellyfish are among the least-appetizing creatures in the oceans. And biologists have long assumed that even other sea creatures didn’t eat them. After all, 95 percent of the average jellyfish is nothing but water, so it doesn’t offer much actual food. And the “stingers” on many jellies can turn them from prey to predators.

Recent research, though, suggests that jellyfish are part of the diets of many marine creatures -- from fish to birds to crabs. Scientists have found new ways to study what these creatures eat. They can find the chemical “fingerprint” of a fish’s prey in its muscles, for example. They can detect the DNA of a bird’s prey in the bird’s droppings. And they can attach cameras to penguins and other creatures and watch them eating.

Those techniques have produced some interesting results. One study, for example, found that jellyfish may account for up to 40 percent of a penguin’s diet -- even when there are lots of dining choices. Another found that jellyfish may account for up 80 percent of the diet of juvenile bluefin tuna. And others have found that scavengers quickly snap up the jellies that fall to the bottom of the ocean.

From these and other results, one team recently concluded that jellyfish might be a major food source after all. They’re easy to catch and digest. And they’re found everywhere -- sometimes in massive blobs that can span miles. So the unappetizing-looking jellyfish may be a common item on the menus of many of the world’s marine creatures.