Taming the Lion(fish)

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Genetics and tracking helps USGS researchers learn where the invasive fish are now – and where they may go next.

Beautiful? Yep.

Dangerous? Absolutely.

Unstoppable? Seems that way.

Armed with venomous spines, a largely non-discriminating palate, the ability to survive in various salinities and depths, and a high reproductive potential, lionfish have invaded the southeastern coast of the United States, and as USGS scientists recently discovered, the fish aren’t done spreading yet.

USGS uses genetics and tracking data to better understand lionfish biology and ecology and to figure out where the fish are – and where they may go next.

Where Did They Come From?

Lionfish have invaded US Atlantic coastal waters, the Caribbean Sea, and the Gulf of Mexico with unprecedented, alarming speed. Though reports of sightings date back to the 1980s, it is only recently that the species has exploded in numbers and range. In fact, the lionfish invasion is the first documented case of a non-native marine fish establishing itself in the Western North Atlantic/Caribbean region.

Image: Invasive Lionfish Removal
A red lionfish (Pterois volitans) waits to be hauled to the surface, where it will be used by NOAA in lab studies on lionfish reproductive biology, age, and growth. Karen Doody, U.S. Geological Survey, public domain

Native to the Indo-Pacific region, the first recorded lionfish sighting in United States waters dates back to 1985; this singular appearance off the Florida coast didn’t raise many alarms. But then another lionfish was reported in 1990. And then another one in 1992. And then a few more were reported in 1995. By the early 2000s, lionfish had successfully invaded southeastern waters.

According to USGS Fish Biologist Pam Schofield, who documents occurrences of non-native marine fishes for USGS’ Nonindigenous Aquatic Species database (also known as NAS), NOAA published a report in 2002 showing lionfish had established a breeding population in the Atlantic Ocean.

“Before that, we had only seen sporadic reports of single fish here or there,” Schofield said. “It seems lionfish had persisted for years at very low densities, and then finally built up enough of a population to become invasive and spread on to other areas.”

The fish is popular as an aquarium species, thanks to its exotic red, brown, and white stripes and long, flowing fins, and was likely introduced via an intentional/accidental release into coastal waters. Though Florida has often been cited as the likely location of lionfish introduction, USGS genetic research suggests more than one introduction has probably occurred, with some introductions occurring at more southern parts of the Caribbean Basin, which stretches from parts of Florida’s Gulf Coast through South America.

With few if any predators regulating its size, the lionfish population has boomed. As they prey in coral reef ecosystems on invertebrates and fishes, including juvenile game fish such as snappers and groupers, the lionfish disrupts marine food webs, impacting its non-native environment.

The lionfish’s reproductive habits may also bolster their successful invasion: females may be able to spawn as often as every four days. This could result in the release of up to two million eggs a year from a single fish. Following spawning, larvae can disperse long distances via ocean currents for up to 35 days.

Image: Juvenile Lionfish
Juvenile lionfish. James Morris, Jr., NOAA, public domain

So, to review: venomous spines + ravenous diet + a lot of eggs released each year + few, if any, natural predators = explosive invasion potential.

Reefs, Mangroves, and Estuaries – Oh, My

Snorkelers, divers, fishermen, or environmental managers in this region can tell you: lionfish have taken over the waters. Available sighting data recorded by USGS complements these anecdotes. The venomous fish have been spotted along the Atlantic coast as far north as New York, throughout the Gulf of Mexico, the Caribbean Sea, and coasts of Central and South America. They’ve also been observed in a wide variety of habitats, including coral reefs, natural hard bottom, seagrass beds, mangroves, and artificial reefs.

USGS tracks lionfish distribution via the NAS database which is a national repository for spatially-referenced sightings for non-native freshwater and marine plants and animals. Lionfish sighting records come largely from the National Oceanic and Atmospheric Administration and the Reef Environmental Education Foundation, as well as other government agencies, university researchers, non-governmental organizations, commercial fishermen, and citizen scientists.

“NOAA and REEF did the majority of data collection early on,” Schofield said. “The role of USGS - NAS is to serve as a clearinghouse for the data and to act as a platform to share this information with the public.”

A high number of sightings come from citizen scientists, an invaluable resource it turns out: when compared to traditional fishery-independent data sources, citizen scientists documented lionfish one to two years earlier and more frequently than traditional reef fish monitoring programs.

The database is publicly accessible, allowing users to view current distributions, search for particular regions and species, and report sightings of non-native and invasive aquatic species. Information from the database is used to generate scientific reports, real-time online queries, spatial data sets, regional contact lists, species information sheets, and occurrence alerts – all important tools for scientists and managers addressing the lionfish invasion.

Watch Out, Pacific Coast

Using life-history and sighting data from NAS, USGS researchers and their collaborators can model where the lionfish might next invade. Recent habitat modeling studies revealed lionfish are likely to expand along the Atlantic coast of South America, perhaps even as far south as Uruguay. Only a few areas along the eastern Pacific Ocean were predicted to be suitable for the species; however, the fish could still potentially establish itself in this region if it were to be introduced. Particular areas of concern include the Gulf of California, the Central American coastline from Guatemala to Panama, the Peruvian coast, and the reefs around the Galapagos Islands. While no lionfish have been reported in these Pacific coast areas, the species is prevalent in the aquarium trade, and there is concern about the likelihood of introduction.

Lionfish Distribution 1995
Lionfish distribution, 1995. Source: nas.er.usgs.gov
Lionfish Distribution 2015
Lionfish distribution, 2015. Source: nas.er.usgs.gov

The researchers also found that species in their native range do not necessarily behave as they would in their non-native range. According to Schofield, knowing where lionfish occur in their native range is not a great predictor of where lionfish will spread to in their invaded range. For example, models using native occurrence data underpredicted the distribution of lionfish in some of the most invaded waters, like the Gulf of Mexico.

“Once an organism is translocated from its native range, all bets are off,” Schofield said. “That’s another reason it is so hard to predict the consequences of invasions.”

Schofield and her collaborators continue efforts to understand the lionfish’s population structure and dispersal pattern and to forecast their spread. They are testing potential eradication/control methods to inform environmental managers in their efforts to combat the invasion. This includes currently working on innovative techniques to detect and trap lionfish.

“One of the most exciting areas of lionfish research right now is the development of novel methods of control, such as lionfish-specific traps,” said Schofield.

But for areas yet untouched by the lionfish, prevention may be key, especially for areas that offer potential suitable habitat.

“If lionfish were introduced on the Atlantic Coast, it is possible for them to be introduced on the Pacific coast,” Schofield said. “This is a warning to scientists and resource managers in California through Central and South America; lionfish have had devastating effects in the Atlantic and Caribbean. Hopefully those will not be repeated in the Pacific.”

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Spotted a lionfish in your waters? Please report it to USGS-NAS.

For more information on USGS lionfish research: https://www.usgs.gov/centers/wetland-and-aquatic-research-center-warc/science/lionfish-distribution-geographic-spread