Barrens Topminnow Project

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 consider the topminnow secure when there are 15 protected populations within the historic range of the species.

In support of this effort, BTMs propagated at Conservation Fisheries Incorporated (Knoxville, TN) and the Tennessee Aquarium (Chattanooga, TN) are being 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.

A total of 1,194 BTMs, grown-out at Dale Hollow NFH, were stocked at three sites in Franklin County, Tennessee in FY 2008. All of the sites are located on private land in the Elk River drainage. The hatchery switched its BTM production focus from the Caney Fork River drainage (Type Locale Population) to the Elk River drainage (Pond Spring Population) in FY 2005. Most of the Caney Fork sites have large populations of Western mosquitofish (Gambusia affinis), a factor which seems to preclude recruitment of young-of-the-year BTMs. There seems to be less of a problem with Gambusia at the Elk River sites. 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 fishes 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.

Competition with Gambusia is not the only threat that BTMs face. The Barrens Plateau has experienced severe drought conditions over the last two years. The type locale (Coffee County, TN), the site containing the population from which the species was originally described, has historically been impacted by drought conditions. This spring-fed pond was recently deepened with a track hoe to prevent the pond from going dry. In spite of this effort, it became necessary to remove over 100 adults and 1,000 juveniles in August 2008 because it was feared that the water level had dropped to a point that there was not enough water to support the present biomass. The rescued fish were transferred to the Tennessee Aquarium for holding. The fish will be stocked back into the site when habitat conditions improve.