Moray eels thrive on coral reefs close to people

Coral reefs that are in close proximity to larger populations of people tend to have fewer sharks and other fish due to higher fishing pressure. But new research shows there’s one group of predators that’s the exception — moray eels.

Scientists from FIU’s Institute of Environment used a combination of video data from Global FinPrint — the world’s first and largest shark and ray survey — and environmental DNA analysis to conduct the largest study in the Caribbean on moray eel populations.

Reefs located closer to humans usually have higher levels of fishing, which depletes sharks and other large predatory fish. Morays, though, don’t taste very good to people and have little commercial value. Not being a good catch works to their advantage.

“Global FinPrint was set up to study sharks but an added benefit was that moray eels also went after the bait. They were often very aggressive, sometimes biting at stingrays, reef fish and even small sharks,” said Demian Chapman, Global FinPrint co-lead and FIU associate professor.

Moray eels are mysterious and notoriously difficult to study. They are usually lurking in even the smallest crevices of coral reefs, stalking their prey — fish, octopuses, crabs and lobsters — and launching a sneak attack from below. This is where the Global FinPrint data became helpful and provided a never-before-seen look at just how common these hidden predators are on certain reefs.

Baited underwater cameras were used to survey 67 reefs in 12 Caribbean nations. On reefs further from humans where sharks and other large predatory fish are still common, morays were less common or stayed hidden for the most part. On reefs closer to people, where sharks and other large predators are fished, the morays were more common and weren’t afraid to creep out and start snapping at anything in the way of a meal.

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