Staff photo by Erin O. Smith / Meredith Harris, a reintroduction biologist with the Tennessee Aquarium Conservation Institute, holds a Barrens topminnow at the Tennessee Aquarium Conservation Institute Monday, October 21, 2019 in Chattanooga, Tennessee. The U.S. Fish and Wildlife Service granted endangered species status to the Tennessee freshwater fish. The Barrens topminnow, which is now nearly extinct, was proposed for endangered species protection four decades ago.

This story was updated at 10:32 p.m. on Oct. 21 with new information.

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Tennessee freshwater fish

The U.S. Fish and Wildlife Service has granted endangered species status to a Tennessee freshwater fish.

The Center for Biological Diversity said the nearly extinct Barrens topminnow was proposed for endangered species protection four decades ago. The fish is found only in central Tennessee in clear, spring-fed Barrens Plateau streams.

"These beautiful fish are finally getting federal protection, but the decades of delay almost drove them extinct," said Tierra Curry, the center's senior scientist said in a statement.

The flashy colored fish grows to 4 inches long and swims near the water's surface, preying on mosquito larvae and other insects.

Captive-breeding populations are being held at the Tennessee Aquarium Conservation Institute in Chattanooga and at the Conservation Fisheries Inc. in Knoxville. The Conservation Institute is the only research facility in the Southeast with a primary focus on saving freshwater animals.

The aquarium has bred and released more than 20,000 Barrens topminnow since 2001 — when the groups held the first release. However, it didn't release fish in 2017 or 2018.

The program has slowed due to the regular ebb and flow of the funding availability and the results of the program. The fish population has struggled to grow to a sustainable population.

The group says the species used to be found at 18 sites, but now exists at five, with none in good condition. Climate change-induced drought, loss of riparian vegetation to pasture and predation by non-native mosquitofish are threats.

The mosquitofish was introduced to mosquito larvae, but it also likes the topminnow larvae and young fish.

The institute and Conservation Fisheries have been working with organizations like the U.S. Fish and Wildlife Service and Tennessee Wildlife Resources Agency to sustain the existing population. The federal listing will open additional funding.

"That's the hope, that [the listing] does open up funding opportunities again," conservation institute program leader Matt Hamilton said. "We were hoping the recovery we were doing would curtail this, but due to mosquitofish and drought, it's just obvious that it needs more."

Hamilton believes the program has been relatively successful, despite needing the federal listing, as the fish would likely be limited to one site without the working group's intervention, he said.

Additional funding would pay for population surveys to track the current size and health. It could also help jumpstart reintroduction efforts.

The institute is currently focused on creating what Hamilton refers to as an "ark population" or "assurance colony." The biologists are breeding the fish to preserve genetic lines and create a diverse gene pool in captivity. That population will be used if the current population continues to decline or becomes extinct in the wild.

The aquarium does not plan to release Barrens topminnow in 2019, largely due to the drought, but hopes to release a small population in Spring 2020.

Barrens topminnow are on display on Level 2 of the Tennessee Aquarium River Journey building at the end of the river gallery in an area aquarium staff refer to as the "tiny but mighty display."