Dale Hollow National Fish Hatchery
Southeast Region
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Barrens Topminnow Project

Barrens topminnow. Credit: USFWS

Barrens topminnow. Credit: CFI

The Barrens topminnow (Fundulus julisia) is an extremely rare fish occurring in springs and spring influenced streams on the Barrens Plateau in south-central Tennessee. Dale Hollow National Fish Hatchery (NFH) is an active member of the Barrens Topminnow Working Group (Group), a conservation coalition dedicated to the protection of existing populations of Barrens topminnows (BTMs) while restoring and enhancing other areas within the species historic range for future reintroductions. The Group will focus on protection and management of the remaining wild populations of the Barrens topminnow, establishment of captive-bred populations, and reestablishment of the species within a significant portion of its historic range in Tennessee.

Many of the locations where BTMs are currently found or have been found historically, have large populations of Western mosquitofish (Gambusia affinis), a factor which seems to preclude recruitment of young-of-the-year BTMs. Competition with Gambusia is not the only threat that BTMs face. The Barrens Plateau has experienced severe drought conditions in recent years. There have been several instances where it became necessary to remove adults and juveniles for holding after spring pools dried up. The rescued fish were held at the Tennessee Aquarium and Conservation Fisheries Incorporated (CFI) until conditions improved enough to stock the fish back out. Dale Hollow NFH now maintains an empty 300-gallon capacity, closed recirculation system in the event that we are asked to help bring fish in from the wild for holding. The reintroduction effort is closely linked to the Service’s Partners for Fish and Wildlife Program (Program). The Program works with private landowners to restore historic habitat types which benefit native fish and wildlife. Fish cannot be reintroduced if suitable habitat does not exist. Every lot of BTMs is screened for disease by the Warm Springs Fish Health Center, Warm Springs, Georgia, prior to transfer between facilities and prior to reintroduction into the wild.

Historically, BTMs propagated at Conservation Fisheries Incorporated (Knoxville, TN) and the Tennessee Aquarium (Chattanooga, TN) have been transferred to Dale Hollow NFH for grow-out and subsequent reintroduction into the wild. Juvenile fish are reared in closed, recirculation systems in order to control water temperature and prevent the spread of disease between various lots of BTMs and other aquatic species being reared at the hatchery. The typical BTM rearing system consists of a 300 gallon capacity circular tank (plastic or fiberglass), outfitted with a sponge filter (driven by compressed air) and two biofilters (trickling filters). Water is circulated from the tank, through the biofilters, and back into the tank with a magnetic drive pump. Fish are fed a mixed diet of frozen brine shrimp, frozen blood worms, and spirulina flakes. The bottom of the tank is covered with aquarium gravel, and green colored mop heads and plastic plants are provided for cover. The mop heads are made of green colored yarn and are intended to mimic the filamentous green algae which is typically a component of good BTM habitat. The grow-out period lasts from six months to one year. Dale Hollow National Fish Hatchery became involved in this program in Fiscal Year 2001.

Release site. Credit: USFWS

Release site. Credit: USFWS

Recirculation system

Recirculation system. Credit: USFWS

A total of 123 Barrens topminnows (2015 year class) were received from the Tennessee Aquarium in September 2016. Eight males and twenty females from this lot were subsequently transferred to CFI for broodstock. An additional forty-two, 2015 year class Barrens topminnows and sixty, 2016 year class Barrens topminnows were received from CFI in June 2017. All three lots remaining at the hatchery are derived from the Elk River population and are being maintained in separate tanks as ark populations. This species has recently been proposed for listing as endangered under the Endangered Species Act (ESA).

Last updated: June 7, 2018