Sharks, grouper learn to prey on lionfish

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By: James Whittaker | james.whittaker@cfp.ky

Research from Little Cayman suggests that large grouper and nurse sharks are starting to prey on lionfish – a potentially game changing development in the Atlantic wide battle against the invasive predator.

A new study which involved lionfish being tethered to lead weights and observed using GoPro video cameras, showed that native species are starting to eat lionfish without them being speared by divers. 

The study showed that predation was over ten times more likely on sites that had been routinely culled by scuba divers, indicating the behavior may have been learned from humans. 

In their study, the researchers from the University of Florida suggest that predators will supplement, but not replace, the efforts of divers to rid the Atlantic of the invasive, voracious predator which is decimating local fish populations across the region. 

“Overall, results suggested that native predators were capable of consuming healthy, tethered lionfish off Little Cayman Island and the naïveté of native predators was overcome by conditioning.  

“Of course, conditioning designed to increase predation on lionfish, augment culling, and help control the invasion must be implemented without endangering people,” wrote the researchers Jessica Diller, Thomas Frazer and Charles Jacoby in the Journal of Experimental Marine Biology and Ecology. 

Culling lionfish in the presence of sharks, eels and barracuda is problematic because it has led to an increase in reports of divers being bumped, and in some cases bitten, by predators as they compete for the catch.  

The lionfish’s rapid population boom in the Atlantic has been attributed to an absence of natural predators.  

It had previously been thought that native fish would only prey on dead or injured lionfish after they had been speared by divers. 

The news that several species are now beginning to hunt lionfish on their own represents a significant breakthrough in the battle to prevent Caribbean reefs from becoming overwhelmed. 

Neil van Niekerk, of Southern Cross dive center which provided logistical support to the researchers, said the results emphasized the importance of culling by divers. 

“What the research shows is that on reefs where we actively cull, predators are learning to hunt lionfish. 

“Predators are eventually going to learn on their own anyway, but that could take 50 years. Our reefs and our dive tourism can’t wait that long.” 

The research project involved 132 lionfish collected from Little Cayman’s reefs, tethered to lead weights with monofilament fishing line and placed at strategic points around the island during the early afternoon. The test fish were split between three habitats – regularly culled reefs, rarely culled reefs, and seagrass where no culling occurred. 

Fish that were missing from cleanly broken tethers the next morning were recorded as “predation events.” Predation was 13 times more likely on culled reefs than on rarely culled reefs and 28 times more likely on culled reefs than on seagrass. 

“The potential for predation documented at our intensely culled reefs indicated that native predators conditioned to eat lionfish killed or injured during culls learned to hunt, capture and consume this novel prey without human intervention,” the researchers wrote. 

Video surveillance at the sites documented nurse sharks and Nassau grouper feeding on the tethered lionfish. 

The researchers acknowledge the process of tethering the lionfish could have made them more vulnerable to predators. But they suggest this was not a major factor, pointing out that the tethered fish deployed their normal defense mechanisms. 

“Videos showed that tethered fish behaved similarly to untethered lionfish by hovering near the substrate within minutes of deployment and employing a typical response to predators. 

“Despite this latter behavior, videos documented predation by nurse sharks and Nassau grouper, with predators not deterred by contact with the venomous spines.” 

Authorities in Jamaica, meanwhile, are reporting more positive news in the lionfish battle. 

Jamaica’s National Environment and Planning Agency is reporting a 66 percent drop in sightings of lionfish in coastal waters, attributed largely to the efforts of cullers and a growing appetite for lionfish fillets.

 

http://www.compasscayman.com/caycompass/2014/04/16/Sharks,-grouper-learn-to-prey-on-lionfish/

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