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Simple trap effective against invasive lionfish, study shows

All photos and video courtesy of Alex Fogg.

A relatively inexpensive and simply designed trap shows promise as a tool for combating the invasive lionfish, according to new research from the University of Florida published in PLOS ONE.

Lionfish, which are native to the South Pacific and Indian oceans, are today found in the Gulf of Mexico, the Caribbean Sea and elsewhere in the western Atlantic Ocean. Like other invasive species, they are a problem for native ecosystems because they have few predators, produce lots of offspring and prey on native species.

Underwater spearfishing is an effective way to reduce lionfish numbers, but scuba divers can only go so deep.

“Lionfish have been observed below 300 meters, but scuba diving is limited to less than 40 meters,” said Holden Harris, lead author of the study and a postdoctoral researcher with the UF/IFAS Nature Coast Biological Station. “In this study, we showed that the Gittings trap, which can be used at lower depths, is an effective way to capture lionfish and doesn’t negatively affect native fish.”

The Gittings trap is named after its designer, Steve Gittings, chief scientist for NOAA’s Office of National Marine Sanctuaries and one of the study’s authors. A Gittings trap consists of netting attached to a circular frame of metal or PVC tubing. The trap has hinges that allow it to open and close like a clam shell.

A Gittings trap open on the ocean floor.

A Gittings trap open on the ocean floor. Credit: Alex Fogg

 

When deployed (see video below), the trap lies open on the ocean floor and features an upright object in the middle — Harris’ experiment used a piece of plastic lattice you might find at a gardening center.

To lionfish, this object resembles a reef — their natural habitat — and they congregate around it (see video below). When the trap is brought to the surface, the hinges close and the netting scoops up any lingering lionfish.

Harris and his team tested the Gittings trap near artificial reefs in the northern Gulf of Mexico. They found that lionfish were attracted to the Gittings traps at rates more than 10 times that of native fish, indicating that the trap would have a minimal impact on native fish if used.

Since Harris’ study required researchers to record the number of lionfish and other species drawn to the Gittings traps, the study tested the traps in shallower waters where scuba could be used. However, the study’s results show that the Gittings trap effectively targets lionfish, an important first step in testing the trap’s performance in various environments.

While the Gittings trap is less effective than spearfishing at removing lionfish, it could function at depths inaccessible to spearfishing scuba divers, Harris said. The traps could be especially useful in the northern Gulf of Mexico, where 90% of the region’s reef habitat — and where lionfish like to hang out — is too deep for scuba. Still, much more work will be necessary to test traps near natural reefs and determine whether catch rates can be high enough to support commercial use.

This newest study on lionfish follows two other recent studies from UF researchers on the invasive species.

A study led by Kristen Dahl, a postdoctoral researcher in the UF/IFAS School of Forest Resources and Conservation Fisheries and Aquatic Sciences program, used an acoustic positioning system to track the movements of lionfish. Tags attached to lionfish pinged the system 24 hours a day, pinpointing the location of each fish within just a few meters. This precise tracking method showed that lionfish roam more broadly and for greater distances than previously thought, demonstrating different movement dynamics than what has been reported in other regions of the lionfish invasion. Understanding lionfish movement has important implications for their ecology, artificial reef management and lionfish control strategies.

Another study led by David Chagaris, research assistant professor at UF/IFAS Nature Coast Biological Station, investigated the impact of lionfish on reef ecosystems in the northern Gulf of Mexico between 2010 and 2014, a span that saw both the Deepwater Horizon oil spill and the first reports of lionfish in the region. Ecosystem models were developed with extensive data collected during the period and  demonstrated the potential for complex responses in disturbed reef ecosystems of the northern Gulf of Mexico. Chagaris and his co-authors found that lionfish slowed the ecosystem’s recovery following the spill.

In collaboration with partners at the federal, state and local level, UF scientists have been studying lionfish behavior, impacts and countermeasures for many years, said William Patterson, a co-author of all three studies and a professor of fisheries and aquatic sciences in the School of Forest Resources and Conservation.

“Lionfish research at UF has had three main goals,” Patterson said. “One, we want to track the number of lionfish and how they move in the environment, which is what Dr. Dahl’s study helps to do. Two, we want to estimate the impacts of lionfish, and Dr. Chagaris’ study furthers our understanding of those impacts. And three, we want to find ways to mitigate the effects of lionfish, which is what Dr. Harris’ new research is exploring.”

In recent years, as the public has become more aware of the lionfish problem, interest in catching and eating lionfish has grown. If the Gittings traps prove to work well in deeper waters, they may one day offer fishermen a new way to harvest lionfish, Harris said.

In the meantime, lionfish face other threats that may curtail their numbers, Harris said.

Earlier this year, Harris authored a study showing that a skin disease affecting lionfish in the Gulf was connected to a decline in their numbers. Other research has indicated that some larger fish, such as sharks, may be eating lionfish, and that lionfish may in fact be eating each other as a result of overpopulation.

Dahl’s study saw evidence of the former. Pings from the sensors used in the study showed 10% of the tagged lionfish suddenly sped out of the study area and disappeared — strong evidence for something big and fast eating the lionfish and swimming away, Dahl said. This evidence of natural predation of lionfish has important implications for controlling their densities and developing a lionfish market.

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