Invasive fish, snakes tracked with high-tech databases, maps, DNA

By Jean Lotus
Invasive fish, snakes tracked with high-tech databases, maps, DNA
The invasive lionfish has spread dramatically and is a voracious eater. Photo by Yinan Chen/goodfreephotos

DENVER, Aug. 19 (UPI) -- Fish scientists on the hunt for non-native species are using an array of sophisticated techniques, including high-tech databases, storm maps and DNA samples to track destructive newcomers to U.S. waterways.

Invasive species with few natural predators can spread like biological wildfires, pushing out native species and permanently changing ecological environments. Invasive species in the United States on land and water are estimated to cost $120 billion per year, according to the U.S. Geological Survey.


At the Gainesville, Fla., Nonindigenous Aquatic Species Program, fish scientists have been gathering data on the locations of non-native water creatures for 30 years, which is now online in an interactive database.

"We track things that live in the water anywhere they're not supposed to, anywhere in the U.S.," said Matthew Neilson, the fishery biologist.

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Photos of unusual fish or other water species can be uploaded by state wildlife managers or the public. An alert system flags a new species discovered in new regions and sends emails to wildlife managers and state departments of natural resources.


"We're trying to give resource managers a warning before some non-native species shows up," Neilson said.

Some of these invaders include Asian carp species, including the bighead, silver and grass carp, which are threatening the Great Lakes and the region's $4.5 billion fishery industry.

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Other disruptive invaders include zebra and quagga mussels and round goby in the northern United States, and the hyper-predator lionfish, which is eating its way up the East Coast as far as Rhode Island and throughout the Caribbean and Gulf of Mexico.

Scientists also are using the tech tools to track destructive giant snails and Burmese pythons, among other creatures.

Storm migration

One way that non-native species migrate is during big weather events like hurricanes in which flooding can move water from one natural watershed to another. A watershed storm mapping system shows where non-native species might move between regions.

For example, after Hurricane Harvey in 2017, the USGS storm mapping system showed that giant apple snails were discovered in Louisiana's Calcasieu River-Bayou, possibly migrating from the Lacassine National Wildlife Refuge to the east, Neilson said.

The large mollusk can reach 6 inches and gobbles up aquatic plants. Originally from Asia, the apple snail has become a major pest in the rice fields of China and the Philippines, according to the Aquatic Nuisance Species task force. East Texas and Louisiana rice crops might be threatened by the apple snails, which also destroy habitat for other native species, Neilson said.


Another method developed for tracking non-native species is biosurveillance that collects environmental DNA, a biological marker that can indicate the presence of a species of animal.

"The eDNA is like the smoke alarm that indicates something's there," said Jon Amberg, a research fish biologist at the Upper Midwest Environmental Sciences Center in LaCross, Wis.

Samplings of eDNA are used to track invasive Burmese pythons in the Florida Everglades and the Loxahatchee Wildlife Refuge, said Margaret Hunter, research geneticist at the Wetland and Aquatic Research Center in Gainesville.

The giant snake species is "cryptic" and sneaky and the Everglades is difficult to work in, Hunter said. A sudden drop in water birds, and mammals like deer, raccoon, fox and hares is attributed to the loose pythons, which are said to have escaped from Miami exotic pet facilities during 1992's Hurricane Andrew.

"We see the severe mammal declines, and even though we can't see the snakes, the eDNA is telling us that they're there," Hunter said. A 17-foot python, caught in April by researchers near the Everglades, weighed 140 pounds and contained 73 developing eggs.

The lionfish in Florida has become such a problem by devouring other fish and reef life that the Florida Fish and Wildlife Conservation Commission offers cash prizes in fishing tournaments to those who catch the greatest number of that species.


Another detection technique is becoming popular. Genetic scientists at Notre Dame and Cornell universities helped develop methods to extract genetic material from waterways by adding enzymes through a process called a polymerase chain reaction that replicates DNA signatures.

"It's been a breakthrough in the past few years where you can extract the DNA right from water and don't have to have the fish in hand," said Michael Pfrender, a Notre Dame biology professor.

Computers analyze an alphabet soup of DNA signatures and flag for specific invasive species, like the Asian carp or zebra mussel, or try to develop a snapshot in time in which animals are present in a waterway.

Also, handheld eDNA detectors can analyze the "bait wells" in fishing boats to detect zebra mussels and their larvae, Wisconsin's Amberg said.

In the mountainous West, eDNA is used to track destructive non-native fish like the northern pike, which were stocked as a sport fish in the 1950s and '60s in Alaska near Denali National Park.

Aggressive predators, pike have spread through the far Northwest in more than 120 lakes, streams and river systems, said Adam Sepulveda, of the Northern Rocky Mountain Science Center in Bozeman, Mont.


"Pike are absolutely decimating native sockeye salmon and cutthroat trout," Sepulveda said. His team uses eDNA filtered by robotic collectors to monitor waters in the Columbia River basin, where native salmon are at risk.

Collecting eDNA also has proved fish scientists wrong, Sepulveda said.

In 2016 and 2017, when large whitefish die-offs on the Yellowstone and Upper Snake rivers were attributed to a pathogen that caused kidney disease, fish scientists using eDNA found evidence of the disease's parasite in other waterways where fish did not die, he said, showing that the problem was more complex than scientists thought.

The USGS is seeking to place eDNA detectors on 8,500 river streamgage sites across the United States, according to a report published Wednesday. The idea would be to develop real-time eDNA monitoring and keep an eye out for invasive species by alerting local wildlife agencies as DNA is discovered.

"We're trying to figure out how to bring the lab to the field and get as close as we can to real-time information so local stakeholders can act quickly," when a destructive non-native species is detected, Sepulveda said.


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