Surveys near Buckhorn Lake leads to discovery of new population of threatened Kentucky Arrow Darter

 The U.S. Army Corps of Engineers Louisville District recently organized a partnership with the U.S. Fish and Wildlife Service, Kentucky Division of Water and the Office of Kentucky Nature Preserves to monitor for Kentucky Arrow Darter populations around Buckhorn Lake in Buckhorn, Kentucky. The Kentucky Arrow Darter is a federally threatened fish species from the upper Kentucky River Basin. 

Surveys from May 2023 discovered a previously unknown population of Kentucky Arrow Darter on fee lands near Buckhorn Lake. Wildlife Biologists Steele McFadden and Jeff Hawkins and Limnologist Zac Wolf led the effort for the Louisville District. 

“Environmental Support Section in Planning has been working for several years to develop a better understanding of what rare species occur on our lake projects. This is critical baseline information that needs to be collected, because it allows us as an agency to make management decisions for the lake that protect these resources and potentially grow them,” McFadden said. “When I first started with USACE nearly four years ago, I was surprised at how little we knew about what actually lives in our lake projects. I think a lot of people just assume that we know what’s out there, but our region is very biologically diverse, especially in Kentucky. You really need boots on the ground looking for these special species and habitats, because so often they only occur in a very small area, and once they are lost it is very challenging to get them back.”

In Fiscal Year 2022, the district received funding to conduct Kentucky Arrow Darter surveys. 

“I reached out to Zac Wolf from our Water Quality team to discuss my thoughts and see if he had any recommendations for the study, and it made sense for us to team up and collect Kentucky Index of Biotic Integrity data at the same time,” McFadden added. “Kind of a way to synergize with the funding and get a win-win for both our teams. We reached out to Mike Compton at the Office of Kentucky Nature Preserves and Mike Floyd at the USFWS and there was immediately a lot of interest in working together on this. It quickly turned into a multi-agency effort.” 

According to the team, the surveys conducted served two purposes, and one of those purposes was to identify locations of fish species that are rare, endangered or threatened that occur on Louisville District property or waterbodies affected by Louisville District operations and activities. 

“Awareness of these locations are important when making considerations on what USACE does so that we can minimize impacts to species of conservation concern,” Wolf said. “This study is special because we already know the Kentucky Arrow Darter occurs in the Buckhorn Lake Basin, but there are many data gaps on where specifically it is around the lake.”

The other reason for conducting these surveys was for the team to determine the overall water quality of the streams that flow into the lake as well as the tailwater downstream of the dam. 
“Measuring the fish community can tell you the quality of the habitat because we know what a healthy fish community should look like,” Wolf said. “If you catch very few species and they are mostly species that are tolerant to pollution, then that indicates poor water quality. If you catch several species including many species intolerant to pollution, then that indicates good water quality. Biological assessments, like this, have the advantage of showing the overall health of the ecosystem over the long-term. Measuring water quality from water samples only captures the quality at a particular time and space. Plus, you actually get to see the impacts on the aquatic ecosystem.”

Several of the streams that flow into Buckhorn Lake were surveyed and KIBI data was collected. The new population discovered was located in a stream that flows directly into the lake and is disconnected from stream-like habitats. Because this species has never been found in lake-like habitats, this new population is likely isolated from populations in other streams and vulnerable to pollution and land use changes that could more easily wipe it out, according to Wolf.

“The KIBI is basically a formula that you plug in your sampling results –how many species you found, how many individuals from each species, how many species that were pollution intolerant, etc.— and it spits out a score that tells you how healthy the fish community is,” Wolf said. “The KIBI can tell you if it’s very good, good, fair, poor, etc.”

With finding this new population, USACE can now better conserve threatened and endangered species on their lands.

According to the Federal Register, the U.S. Fish and Wildlife Service determined the Kentucky Arrow Darter (Etheostoma spilotum), a fish species from the upper Kentucky River Basin in Kentucky, as a threatened species status under the Endangered Species Act of 1973.