If there's one lesson that the ocean is determined to teach us it's that there's always a bigger fish.

On a recent expedition off the coast of South Carolina, researchers from the National Oceanic and Atmospheric Administration (NOAA) used a remote operated vehicle (ROV) to capture footage of a school of sharks tucking into a 2.5-metre (8-foot) swordfish on the ocean floor. It's the sort of thing that's rarely witnessed and the crew were understandably giddy.

But the ocean depths weren't done dishing out the goods just yet.

As they watched the sharks feasting, a wreckfish emerged, lurking on the fringes of the frenzy. With most of the sharks preoccupied with their meal, the wreckfish made it's move. Using the ROV as cover, the hefty fish waited until one of the sharks swam within striking distance before snaffling an easy meal. Sharks may be apex predators in certain habitats but, in this case, it's a different predatory fish that came out on top.

"The wreckfish appears unable to feed on the swordfish directly itself," explains Mystic Aquarium's senior research scientist Peter Auster in a blog post for NOAA. "But by joining the sharks, it was able to feed on an animal that was." Its prey was most likely a Genie's dogfish – a small species of deep-sea shark in the family Squalidae. Genie's dogfish and roughskin dogfish – the larger species of shark also seen getting in on the feeding frenzy – are found along the US continental margin at depths of about 213-610 metres (700-2,000 feet).

"Normally we don’t see any deep-sea sharks in a group or aggregation, unless there is some nearby patch of food," Auster explains. "As relatively small apex predators, they spend a great deal of time searching for prey. When a large food fall occurs, like a 250-plus pound swordfish, the ability to detect and locate the food, and then maximize food intake, is the key to growth and survival."

The footage was captured live as part of the Windows to the Deep 2019 expedition – a "telepresence-enabled ocean exploration" with the goal of learning more about the deepwater areas of the southeastern United States. So far, NOAA have discovered mounds of reef-building corals and explored the methane seep field off Bodie Island. The shark feeding frenzy, however, raises more questions that it answers.

"How do sharks and other species detect large food falls? It could be chemical trails, the vibrations of prey struggling, or the sound of one or more predators who initially found the prey and started feeding," Auster ponders. "This rare and startling event leaves us with more questions than answers, but such is the nature of scientific exploration."


Header image: NOAA's National Ocean Service