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USGS Tracks How Hurricane Floodwaters Spread Non-Native Freshwater Plants and Animals

April 23, 2018

Hurricanes Harvey, Irma, Maria, and Nate may have spread non-native freshwater plants and animals into new water bodies, where some of them can disrupt living communities or change the landscape.

An image of a Giant Applesnail
This invasive Giant Apple Snail is just one of hundreds of non-native aquatic species that might have migrated to new areas due to flooding that occurred during the 2017 hurricane season. Photo by Cayla Morningstar, used with permission. 

To help land managers find and manage these flood-borne newcomers, scientists at the U.S. Geological Survey have created four online maps, one for each hurricane. These “storm tracker” map sets, on which users can see the potential spread of any of 226 non-native aquatic plant and animal species during the 2017 hurricane season, are available at

More than 1,270 freshwater aquatic species have been reported as found beyond their home ranges nationwide. Some have caused no obvious ill effects on their new habitats. Others, like the zebra mussels introduced into the Great Lakes, have caused damage to fisheries, shipping, water utilities and other industries. 

Storm surges and floodwaters can quickly spread non-native aquatic species into waterways where they weren’t found before. They can even create temporary freshwater zones in saltwater environments, as Hurricane Harvey did in parts of the Gulf of Mexico, said biologist Pam Fuller, the leader of USGS’s Nonindigenous Aquatic Species Program.

“USGS’s stream monitoring showed that as the rivers carried Hurricane Harvey’s floodwaters downstream, a freshwater area developed along the Gulf Coast in parts of Texas and Louisiana,” Fuller said. “Normally the Gulf acts as a saltwater barrier that blocks freshwater species from moving along the coast. But that barrier was temporarily gone, and freshwater aquatic species could move into new habitats.”

“Land managers have been responding to all sorts of hurricane impacts,” Fuller said. “It’s hard for them to survey all the places where flooding or storm surge occurred. Our results can help them concentrate on areas where non-native aquatic species are most likely to appear.”

"The U.S. Geological Survey's Flood and Storm Tracker maps are terrific tools we now have available to help determine the spread of aquatic invasive fish, wildlife and plants caused by major storms like the hurricanes we had last fall," said John Galvez, who leads the Peninsular Florida Fish and Wildlife Conservation Office for the U.S. Fish and Wildlife Service.  "The county-by-county maps are helping us make better decisions about where to target surveys and identify ways to eliminate the invaders before they get a foothold in new areas."

Fuller’s Gainesville, Florida-based research group maintains the Nonindigenous Aquatic Species database, the nation’s most complete record of freshwater plant and animal species found outside their native range. The researchers used the nationwide database to identify all the non-native plant and animal species known to occur at storm-flooded sites. Then they modeled the flood waters’ height to identify places where floodwaters overtopped the barriers separating water bodies. The storm trackers show where lakes, rivers, streams and other waterways merged, giving aquatic species the opportunity to spread.

The Hurricane Harvey tracker was the first map set of its kind, said Fuller, whose research team developed all the storm trackers.  “The tracker gives us a realistic picture of whether a particular species may have been introduced into new watersheds by Harvey’s flooding, and where that introduction may have taken place,” said Fuller. “The U.S. Fish and Wildlife Service is using it to decide where to conduct field surveys at national wildlife refuges in Texas and Louisiana.”

Fuller said the sailfin armored catfish (Pterygoplichthys sp.), a South American species sold in the aquarium trade as “Plecos” and found in Houston’s Buffalo-San Jacinto watershed, is one species that may have spread with Hurricane Harvey to watersheds around Galveston Bay. Male sailfin armored catfish dig burrows into canal and river banks, where the females lay their eggs. Large populations of the non-native species can cause canal and river banks to erode or fail, so the species’ spread has the potential to exacerbate ongoing Gulf Coast marsh erosion.

A map shows the potential the area paraná sailfin catfish could have spread around Galveston bay after Hurricane Harvey.
This screen shot of a “storm tracker” map shows the potential the area sailfin armored catfish could have spread around Galveston Bay during the flooding caused by Hurricane Harvey. USGS photo. (Public domain.)

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