In estuaries across Louisiana, scientists are working to collect information about spotted and alligator gar in a non-lethal way — a game-changer for the scientific community — to see how native floodplains and habitats are doing.
These results have culminated in a new study published in Transactions of the American Fisheries Society.
Both spotted and alligator gar, freshwater fish found in the Mississippi River drainage basin and other parts of North America, have typically been used for research into how a habitat is doing through isotope analysis, in which scientists look at the fish’s muscle tissue or stomach contents.
But that method kills the fish, said Thea Fredrickson, lead author of the new study. She now works as an aquatic biologist in Austin, Texas, but started this work in 2018 as part of her thesis during her time as a graduate student at Nicholls State University in Thibodaux.
“It just kind of got me thinking about whether there are ways to do this so that it wasn't a lethal method, such as using fin tissue instead of muscle tissue,” Fredrickson said. “I like to think that I'm a part of a solution.”
Nicholls State University is home to the GarLab, led by fish ecologist and assistant professor Solomon David and students with research focusing on the ecology of migratory and ancient fishes.
David, another author of the study, said the new method involves taking small samples through fin clipping. The gar can quickly grow back their fin tissue, he added, and they also tag the animals to track them over time.
In Louisiana, gar are common fish, even considered as “trash fish” by some people due to a perceived lesser value than more common game fish like bass or trout. But Fredrickson hopes to change these preconceived notions through their work.
“I like the idea that we're changing that perception and trying to get people to care about them,” Fredrickson said.
While overall marked as species of least concern, local extinction exists in the fish in the northern part of their range, such as Ohio, Illinois and the Great Lakes region. By conducting this study in more abundant populations, scientists hope that this non-lethal tool enables sampling in more vulnerable populations outside of Louisiana.
“The fact that we can do this without killing the fish is a big win,” David said. “Anytime you can collect scientific data without having to sacrifice the animal, especially sensitive populations with very large and very old individuals, is beneficial.”
Through fin clipping, David said scientists are finding out how the gars’ diet changes throughout the year to how different fish populations vary depending on location.
Looking at the alligator gar is like a blast in the past. The gar family have existed for around 159 million years, with species that can live for many decades. They serve as good markers showcasing how their habitats are doing.
With spotted gar, these fish are good indicators of healthy ecosystems and populations. Gar can also help with translating genetic information from more commonly-used fishes for applications in biomedical research.
The scientists are also working with the Nature Conservancy and Louisiana Department of Wildlife and Fisheries using information gathered from the gar fish as a way to see how different floodplain restoration efforts are going.
Floodplain restoration is important in Louisiana because it creates spaces to filter and store water, can help with resiliency against storms and land loss and supports biodiverse ecosystems.
“We want to use gars as an indicator of how restored floodplain habitats are being used, and how these important ecosystems might change over time,” David said.
