Thought to be introduced to the U.S. coast via Florida pet owners, voracious lionfish are a growing concern, swimming through the Caribbean and Gulf of Mexico up the eastern seaboard on fins like fairy wings. They arrive hungry and in force. Lionfish eat vulnerable grouper and snapper, and a single invasive fish can spawn up to 30,000 eggs every four days. As widespread as the fish are, most sharks won't readily chow down on lionfish. Instead, divers have now taken to hand-feeding reef sharks lionfish, kebabbed on the end of spears, all in the name of conservation.
Diver Andrés Jiménez and photographer Antonio Busiello describe the practice to the Washington Post: a speared lionfish is proffered to a shark, who swallows the fish head-first, minimizing the chance of getting pricked by a spine. The sharks "are really mad for dead or injured lionfish, and they get used to being fed lionfish by divers," he tells the Post by email.
But there's limited evidence that the sharks will eat the fish without the divers' help. And when humans bring food to wild animals, there's more than a free meal at stake. Feeding wildlife stunts young animals' hunting skills, attracts more animals to certain places and creates an association between humans and food, points out wildlife rehabilitation group PAWS.
Sharks are more intelligent than most people give them credit for, says David Shiffman, shark biologist and graduate student at the University of Miami, to The Dodo. He points out they're certainly capable of forming associations. Captive blacktip sharks, for example, have linked geometric shapes with food. (A recent study in the Open Journal of Animal Sciences offers some of the first evidence that a wild whitetip shark frequently hand-fed by snorkelers in Egypt was involved in three attacks on humans; the conclusions of this study are under dispute, however, and the journal has come under fire in the past for questionable practices.)
Nearly 20 years ago, Florida Museum of Natural History shark expert George Burgess cautioned that "shark-feeding dives freely violate several of the axioms of conventional wisdom advocated by virtually all attack researchers," considering the risk of injury and ecological disruption.
How do we solve the lionfish equation? Canadian and American marine biologists wrote in the journal PLOS ONE last July that one solution is obvious - as the root of the lionfish's spread lies with humans, it's up to us, not predators who won't eat them. "Active and direct management, perhaps in the form of sustained culling, appears to be essential to curbing local lionfish abundance and efforts to promote such activities should be encouraged."
This post has been updated to clarify the evidence that sharks can form associations between signals and food.