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Tennessee Wildlife Resources Agency
Ellington Agricultural Center
440 Hogan Road
Nashville, TN 37220
(615) 781-6500
Helping the Nashville Crayfish Persist in an Urban Setting

The Nashville Crayfish (Orconectes shoupi) is an endemic species to the Mill Creek Watershed, located in Davidson and Williamson Counties. It can be distinguished from other crayfish species by their elongated pincers with red tips and the light colored saddle on its back.

Because the Nashville Crayfish is only found in this watershed, this species was listed as endangered in 1986 under the Federal Endangered Species Act of 1973. The limited distribution of this Nashville crayfish makes any changes to hydrology or land use, including dams, in the Mill Creek Watershed detrimental to the Nashville Crayfish population.

However, recent studies have shown that the Nashville Crayfish is more of a habitat generalist than specialist. It will always experience threats due to its limited range, but it has demonstrated a high degree of resilience to the various disturbances that have occurred in the Mill Creek Watershed. Biologists have estimated that even under the worst case scenario, the population will likely persist. Unfortunately, we don't have historical information to know what the population looked like before all the alterations in the watershed occurred. The Culbertson Dam, located in the Mill Creek Watershed, is one of those alterations.

Gene Flow

The true history of Culbertson dam is unknown, and its purpose may have been transportation or agriculture. However, this dam, located by the newly developed Lennox Village, severely limited the connectivity of the watershed, which meant that the population of Nashville Crayfish was likely fragmented. Fragmentation limited the gene pool reducing fitness (i.e. the ability of organisms to survive and reproduce in the environment in which they find themselves).

Without gene flow between populations a species' gene pool becomes less diverse. This means that any environmental disturbances will have a greater potential for doing significant damage to the species.

On June 4, 2018, the Aquatic Habitat Restoration crew from the U.S. Fish and Wildlife Service began to tear down the Culbertson Dam. Those who have studied Nashville Crayfish believe this dam removal is a positive thing for the species. As Glenn Rohrbach from the Nashville Zoo stated, "It's really important to protect the habitat of this crayfish in Mill Creek, and one of the ways we can do that is removing old unnecessary structures such as this dam." Prior to dam removal, conservation partners gathered to collect as many Nashville Crayfish as possible at the dam site and move them away from the work area.

Aquatic Connectivity

Glenn believes that the removal of the Culbertson Dam "will help not only the crayfish but also the many other different wildlife species that live in Millcreek because removal will restore more natural flow in the creek."

David Withers, from The Tennessee Department of Environment and Conservation, also emphasized the benefits of this project stating, "The dam removal is very important because a lot of habitat upstream of this dam is suboptimal for the crayfish. It has been backed up significantly through the years, so this dam removal is going to provide some fantastic connectivity between populations further upstream in Mill Creek and those already downstream right next to the dam."

The removal of the Culbertson dam, a project managed by the Cumberland River Compact, will not only increase connectivity between species but will also improve the sediment transport and temperature regimes of the Mill Creek Watershed.

View or download a Nashville Crayfish illustrated factsheet with photos.

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