In spite of its highly efficient stinging cell system, the jellyfish has a number of predators: penguins, albatrosses, tuna, swordfish, and many other lesser known fish.
For a hungry fish, biting a jellyfish should be a big disappointment. These gelatinous animals are composed of 95% water. At equivalent volume, they provide three times less calories than a portion of celery. No wonder marine biologists have long considered jellyfish to be an insignificant part of the ocean’s menu.
But there are some species that eat them daily.
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Do fish eat jellyfish?
Until now, we thought that because of their low nutritional value, jellyfish were of no use to the food chain. In addition, research has sounded the alarm that jellyfish numbers are exploding due to climate change, overfishing, nutrient runoff and marine habitat modification.
Jellyfish may have low nutritional value, but this is offset by the fact that they are present in large numbers and easy to catch. In a way, jellyfish are the snacks of the oceans.
The composition and size of jellyfish vary greatly. Some, like the Portuguese Galley, are a composite of different organisms living in symbiosis, not a single individual. Others are so tiny that even the smallest sea creatures and fish will eat them.
What fish eat jellyfish?
Some jellyfish feed on fish larvae and eggs, but the reverse is also true, says the biologist. Sometimes young fish get underneath large gelatinous creatures, such as ray jellyfish.
These offer some protection, as well as a nourishing meal of almost pure protein: indeed, sneaky fish can remove and eat the “big gonads” of jellyfish, which sometimes exist in large quantities in this species. There is a lot to eat in a jellyfish, besides the simple transparent bell that everyone thinks of.
The insignificant number of calories that jellyfish provide is not the only reason why they were overlooked by scientists. When dissecting fish or examining bird droppings, biologists almost never found jellyfish remains. There were exceptions: leatherback turtles and sunfish.
It has long been known that they gorge on jellyfish – they can gobble up several hundred each day. But these predators are extremely large: leatherback turtles can weigh over 900 kilograms, and sunfish 2 tons. Many researchers believed that these animals had adapted their feeding habits to their.
Climate change issues with jellyfish
Chances are that an additional food source is a good thing for turtles and other animals that eat gelatinous plankton. However, adding jellyfish to one’s diet can pose some risks.
For example, leatherback turtles have been observed chewing on plastic bags, thinking they were jellyfish. It is estimated that more than half of the sea turtles have ingested plastic. One study estimates that 14 pieces of plastic can kill a turtle. This may limit the population growth of these already vulnerable animals.
Some species of penguins are also beginning to see jellyfish as an alternative food source. These birds have traditionally relied on krill, which live below the ice caps. But as parts of Antarctica warm, that habitat is shrinking, as is the ice pack. While jellyfish can provide penguins with food when krill is not in sufficient supply, a diet based solely on eating jellyfish will not be possible for all species.
A specific metabolism is required, such as that of a leatherback turtle. For other species, jellyfish are sort of the fries of the ocean, and if their traditional food is completely replaced by these gelatinous creatures, they will be affected.