FGCU scientists study lionfish in effort to eradicate invasive species

Lionfish are beautiful and all-too-plentiful non-natives that people wish would just go away.

Emma DeRoy, a graduate student at the University of Windsor in Ontario, Canada, is observing live lionfish at Florida Gulf Coast University’s Vester Marine Field Station in Bonita Springs to understand the species’ feeding behavior – lionfish are a major threat to any marine environment they invade because they eat vast quantities of juvenile native fishes, including economically important species such as snappers and groupers.

With lakes St. Clair and Erie the closest large water bodies to Windsor, DeRoy became interested in lionfish through undergraduate course work and wrote a research paper on the species. When the time came for her to do her master’s thesis, she decided to study lionfish in Southwest Florida, where one of her biggest challenges was the summer heat – the average high temperature in Windsor during July is 82 degrees, and the average low is 62, compared to Southwest Florida’s average July highs and lows of 92 and 75.

“Lionfish are a model invasive species,” said DeRoy, who has been living and working at Vester since April. “They’re generalist feeders. They have a wide range of physiological tolerances. A lot of research has been done on invasive freshwater and terrestrial invasive species but not on marine invasive species. I’m trying to use feeding behavior to understand the impacts of lionfish, and that could be translated to other invasive species.”

Natives of the Indo-Pacific, lionfish were first reported off Florida in 1985, probably the result of aquarium releases. Since then, lionfish, which have few known natural predators and reproduce at an alarming rate (females can spawn every four days and produce 2 million eggs a year), have spread in huge, voracious numbers throughout the Western Atlantic, including the Gulf of Mexico.

For her study, DeRoy needs live lionfish, so field station manager Bob Wasno and a rotating team of divers have been capturing them in 90 to 100 feet of water at the Captiva Blue Hole, 30 miles off Redfish Pass.

Capture protocol, devised by Wasno and DeRoy, is simple: Lionfish don’t spook when approached by divers, so the lionfish team just swim up to them and catch them between two short-handled nets. Then the lionfish are put into a cage (designed by Wasno) on the sea floor and slowly brought to the surface.

Back at Vester, DeRoy observes, among other things, lionfish attack distance (the distance the fish travels to catch its prey), which “adds another dimension to understanding feeding ecology.”

Such information could lead to further research about feeding and prey-capture techniques of other invasive species.

DeRoy is also looking at how lionfish density (the number of lionfish in a given area) affects feeding dynamics.

“Are lionfish better hunters in groups?” she said. “Some studies have suggested that lionfish hunt cooperatively, but when you get a higher density of predators, sometimes they compete for prey, so that each predator ends up with fewer prey items when hunting in groups. So, with lionfish, does cooperative hunting increase consumption?”

To test the effects of density in feeding, DeRoy will put different numbers of lionfish in a tank and feed them specific numbers of prey items (small fish and shrimp).

“Invasion biologists have done a lot of research on the impacts of invasive species,” DeRoy said. “But we still don’t really understand the scope of their impacts because the impacts are often subtle, they change over the invaded range, or they’re delayed, which makes them difficult to quantify and predict. This is especially the case with marine invaders.”

DeRoy’s research, which is being funded by the Natural Sciences and Engineering Research Council of Canada, can fill in some of the gaps concerning impacts of invasive marine species.

“Better understanding their impacts is key in mitigating their threat and developing appropriate management strategies,” DeRoy said.

For more information on this project and one on research efforts to save the endangered smalltooth sawfish, go to https://fgcu360.com/2017/10/wishes-for-fishes.