Can Sharks Learn to Hunt Lionfish?

Until the 1980s, the Indo-Pacific lionfish did not live in the Atlantic or Caribbean. But then at least one, perhaps a pregnant female - which can produce as many as two million eggs a year - ended up in the Atlantic, probably off Florida, thanks to humans. Some think an aquarist tossed it in. Others speculate a hurricane demolished a home aquarium, and the fish escaped. Regardless of how it got introduced, it found itself in waters where it had no natural predators, and nearly four decades later, the population is running amok.

After just four decades, lionfish are thriving throughout the Atlantic and the Caribbean, from The Bahamas to Belize, from Bermuda to Brazil. They live on shallow reefs down to depths unapproachable by scuba divers and are devouring the endemic fish that don't recognize them as predators. It's a mess.

Is There an Answer?

Some well-intentioned and experienced divers are trying to introduce the lionfish to possible local predators.

The Washington Post reports that in Cuba's Gardens of the Queen National Park, dive guides are spearing lionfish and feeding them to waiting reef sharks hoping that they'll develop a taste for them, spines, and all. The same is happening at other diving locations in the Atlantic/Caribbean area.

Spoon-feeding sharks is the latest desperate attempt to restore the balance of an ecosystem that humans threw out of whack 35 years ago. Sharks may be one of a few animals that can choke down a lionfish. To avoid the toxic spikes on its back and tail fin, they eat the fish head first.

All well and good, until it seems that sharks may be now associating divers with the free handout of food instead of hunting the live fish on their own. Just like pigeons in the park or bears and garbage cans.

In the Indo-Pacific, where lionfish are native, groupers, among other fish, help keep their population in check. Taking a cue, some folks in Grand Cayman have tried to encourage groupers to hunt lionfish by feeding them speared fish but ended up with food-dependent groupers and some aggressive sharks. Neither species seemed inclined to hunt live lionfish.

We've received many reports of sharks following divers spearing lionfish but no reports, until now, of sharks attacking the live fish. In response to a request for information, Christa Minks-Brown wrote on Facebook, "I've seen reef sharks eat live lionfish at the Austin Smith wreck in the Bahamas with no spearing or intervention required." She says her dive buddy Lisa Griffith-Speed has a video.

Long-time Undercurrent correspondent Bill Schlegel (MO) told Undercurrent that divers are attempting to train nurse sharks to hunt and eat lionfish in the Bay Islands of Honduras. These attempts have demonstrated some success, which he witnessed during a November visit to Roatan and Guanaja.

He says, "There is good reason for caution. Environmentalists and others warn that there may be unanticipated and sometimes disastrous side effects when humans mess with mother nature. Previous episodes of teaching sharks to associate humans with food to [attract traveling divers] have been good examples. Both positive - increased awareness of the plight of sharks in general - and negative outcomes have occurred around the world."

Anyone who has attended a hammerhead feeding dive in the Bahamas' Bimini will confirm that nurse sharks are quick learners when it comes to the opportunity for an easy meal. The same can be said of the schooling nurse sharks of Alimathaa in the Maldives, which have learned that fishermen cleaning their catches and dumping the waste in the water equates to plenty of free food.

A Bay Islands divemaster at CoCo View Resort named Raymel mentioned to Bill that because of the drop in dive tourism from the COVID pandemic, he and his associates would hunt lionfish and feed them to the local nurse sharks. Having learned to associate the divers with food, the sharks would turn up whenever the divers were hunting. Now that the tourists are back, the big nurse sharks are all around them, resulting in happy sport divers.

Most important, Raymel said he has begun to observe the nurse sharks actively hunting lionfish independently. He has seen them go into places where they hide, like under overhangs or crevices and aggressively pursue them. He wonders about the long-term outcome of this success with lionfish control, or unforeseen environmental side effects.

It's Best Not to Mess with Mother Nature

People with some expertise on the topic are wary of the outcome. Lad Akins, formerly of REEF and currently Curator of Marine Science at Frost Science (Miami, FL), says, "Constant conditioning at a shark feeding site with trained personnel using tried and true methods with dead food is one thing and certainly an attraction that the dive industry has evolved into a great guest experience.. Hunting, spearing, and feeding wounded lionfish to predators is a different scenario. While it may seem exciting to some, it certainly creates a large potential for unsafe interactions with these predators.

"If sharks, grouper, barracuda, and eels are going to control lionfish, they certainly don't need humans teaching them how to hunt and eat.And if divers are going to control lionfish, they certainly don't need to contend with the aggressive behavior of predators looking for a handout."

Peter Hughes, who used to run lionfish education trips with Akins, concurs. "Local dive shops promoting the dangerous practice of teaching nurse sharks (or any other predator) to hunt lionfish once resulted in a severe wound to one of our guests and many near misses on most trips."

Nicola Smith, a Ph.D. researcher at Earth Oceans Research, University of British Columbia, whose research we featured in our last issue, says, "I strongly disagree with trying to train sharks to eat lionfish. Aside from the negative effect of having sharks now associate humans with food, which can be dangerous, these sort of efforts are not likely to scale up to control lionfish populations on a regional level."

So, while some divers think they can intervene in the underwater food chain to teach new behavior to sharks, the advice of experts is to let the animals figure it out. It's folly for humans to think only good will come of their efforts.

Ben Davison