New Hunting Grounds: Jellyfish Attract Small Fish for Birds to Feed On

Jellyfish may have managed to dodge the environmental bullet for just now. While climate change has vast impacts on marine environments, jellyfish seem to be thriving in warmer waters and growing into large stinging masses that span as much as 30,000 square miles.

These masses, known as jellyfish blooms, led researchers from the United States and Japan to investigate the potential threat of these sea creatures. Their findings, published in Biology Letters, suggest that the jellyfish might have a few unexpected benefits.

According to a news release, previous research had found that small fish sometimes gather among the tentacles of larger jellyfish to feed on the plankton trapped among the tendrils, or hide from predators behind their stinging tentacles. The researchers observed that diving seabirds might be able to find a concentrated source of food among the fish in the tentacles. 

On St. George Island, off the coast of Alaska in the eastern Bering Sea, the scientists strapped video loggers to eight diving birds called thick-billed murre and tracked them in patches of water filled with northern sea nettle, also known as the brown jellyfish. They found that only four birds dove beneath the surface of the water while the cameras were recording, and they encountered jellyfish on 85 percent of the recorded dives. From this they were able to prove that the birds approached jellies and plucked fish from their tentacles in almost 20 percent of the feeding events recorded, which is a relatively high number for a previously unobserved behavior.

This study suggests that the behavior may be a common adaptation for diving seabirds. According to the authors, this supports their hypothesis that jellyfish blooms might actually increase feeding opportunities for seabirds. 

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