The prehistoric-looking lake sturgeon swam up and down the Tennessee River until 1961, when they disappeared.
"We lost our native river giant," said Bernie Kuhajda. "... But, for 15 years, we have been working to bring them back to the river."
Kuhajda, a biologist with the Tennessee Aquarium Conservation Institute, is part of a team that has already brought 150,000 sturgeon back to the Tennessee River. And on Friday, national Endangered Species Day, aquarium staff released eight more lake sturgeon into the river.
The fish released Friday are only about 20 inches in length but can grow up to 9 feet long, weighing 275 pounds. It's common for them to live more than 100 years, aquarium officials say.
Lake sturgeon are listed as endangered in Tennessee and considered vulnerable worldwide. The fish became extinct in the Tennessee River decades ago due to overfishing, dam construction and increased pollution. According to Tennessee Aquarium officials, increased government fishing regulations and the Clean Water Act made the river suitable again for the fish to live here.
The sturgeon the aquarium is introducing into the river come from the Great Lakes and have to adapt to the South's differing environment. Most of the research that has been done on sturgeon is focused on those living in the Great Lakes, Kuhajda said, and researchers are unsure if the fish will show the same behaviors here.
"There are a lot of unknowns and tons of fun research we can do for years to come," he said. "It's a new frontier to have sturgeon back down South."
In order to track those behaviors, the sturgeon released Friday have sonic tags that "broadcast" unique signals, allowing researchers to track them as they move between Knoxville and Chattanooga. There are 29 separate receivers that can track a sturgeon's signal from up to 500 meters away, officials said.
The fish released Friday increase the number of surgically implanted sturgeon in the river to 57.
Researchers will download the information from the receivers every couple of months and can track the fish as they move throughout the river. Those who take a ride of the Tennessee River Gorge Explorer will be able to become citizen scientists, said Grace Mynatt, a naturalist who works on the boat.
"This is a new thing for us," Mynatt said. "People will be able to watch on screen as the receiver picks up signals from any tagged fish nearby."
Reintroducing sturgeon to the Tennessee River is more than just research for Kuhajda -- he calls it the moral thing to do.
"Every time you remove a species from an environment it is like removing a brick from the foundation," he said. "The fish were here and we messed it up. ... We should also help bring them back."
Contact staff writer Kendi Anderson at kendi.anderson@timesfreepress.com or 423-757-6592.