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A bright green irrodescent fish in a small blue net.
Information icon Barrens topminnows are small, colorful fish that live only in a few springs and creeks in central Tennessee. The U.S. Fish and Wildlife Service has proposed listing the fish as endangered. Photo by Emily Granstaff, USFWS.

Barrens topminnow

Fundulus julisia

The Service published a final rule in October 2019, adding the fish to the List of Threatened and Endangered Species. The rule takes effect in November 2019. Current populations are facing issues including habitat alteration; over using topminnows as bait fish; disease and predation; and other natural or manmade factors. Due to the rapid decline of the topminnows, a Barrens Topminnow Working Group was formed in 2001. Group members consist of governmental and non-governmental conservation organizations. In addition to dedicating protection of existing populations of topminnows, the working group is also committed to the protection of existing populations of topminnows while restoring and enhancing other areas within the species’ historic range for future introduction. The program is coordinated with Conservation Fisheries Inc. (CFI), the Tennessee Aquarium, Tennessee Wildlife Resource Agency, USFWS Cookeville Field Office and private landowners through the Partners Program.

Appearance

The Barrens topminnow is a small colorful fish that grows to almost four inches long. It has an upturned mouth with a flattened head and back. Fins are rounded with the unpaired fins set far back on the body. Reproductive males show an array of bright colors of blues, greens, with reddish orange spots and yellow fins. Females, juveniles and non-reproductive males are duller in color with pale brown bodies sprinkled with darker spots on the sides.

Habitat

Its habitat is restricted to springhead pools and slow flowing areas of spring runs on the Barrens Plateau in middle Tennessee. They are strongly associated with abundant aquatic vegetation and will occasionally shelter under overhanging terrestrial plants and tree roots. They have only been found in streams where the predominant source of base flow is groundwater. Temperatures in these habitats are relatively stable, ranging from 59 to 77 degrees Fahrenheit. Although the Barrens Plateau has several spring systems, not all of them are inhabited by the topminnow. In times of drought, if the spring discharge is severely reduced, the topminnows will likely move further downstream into more permanent suitable habitat if available.

Diet

Barrens topminnows are a generalist feeder; they mostly feed on microcrustaceans and immature aquatic insect larvae. They also consume small snails, ants and other insects that fall or wander into aquatic habitats.

Historical range

The Barrens topminnow was originally found in Cannon, Coffee and Warren counties of Tennessee in three river systems, the Elk, Duck, and Caney Fork rivers. These small streams and springs inhabited by the topminnow in each river system are separated by hundreds of miles of intervening, unsuitable, larger stream habitat. Due to the lack of connectivity between these springs, individual populations were isolated, preventing topminnows from coming into contact with one another and moving downstream. Within these systems, the topminnows were known to occur in at least 18 sites. It is thought many more sites were occupied but weren’t surveyed due to lack of access to private land or were modified and were not compatible.

Current range

Habitat is restricted to springhead pools and slow-flowing areas of spring runs on the Barrens Plateau in middle Tennessee.

Tiny minnow-like fish acclimating to the stream temperature by placing the plastic bag in which they were transported into the stream.
Barrens topminnows being acclimating to the stream. Photo, Erin Johnson, USFWS.

Conservation challenges

There are a few conservation challenges facing the Barrens topminnow. One challenge is the introduction of the Western mosquitofish, which eats very young Barrens topminnow. Mosquitofish are aggressive; in aquaria, they have been observed harvesting juveniles and consuming larval Barrens topminnow. Being livebearers capable of producing several broods per year, Western mosquitofish rapidly overwhelm low-density Barrens topminnow populations, especially in small springs.

Drought has also played a role in conservation challenges. As the Barrens topminnow are found in shallow pools they are very susceptible to drought conditions. Because topminnow sites are isolated from one another they are unable to move to different locals without access streams.

How you can help

You can help the topminnow by keeping waterways clean of garbage. Protect riverbank zones where the topminnows live by erecting fencing to keep from degrading shore lines. Refrain from moving other fish species, i.e the Western mosquitofish, into areas they are not known to inhabit.

Subject matter experts

  • Tennessee Aquarium
  • Conservation Fisheries Inc (CFI)

Designated critical habitat

The Service determined that designation of critical habitat was prudent but not determinable at this time because specific information needed to analyze the impacts of designation was lacking. We are still in the process of assessing this information and plan to publish a proposed rule to designate critical habitat for the Barrens topminnow in the near future.

Federal Register notices

The following Federal Register documents were automatically gathered by searching the Federal Register Official API with this species’ scientific name ordered by relevance. You can conduct your own search on the Federal Register website.

  • We're sorry but an error occurred. Visit the Federal Register to conduct your own search.

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