Barren’s topminnow (Fundulus julisia)
|Size||Length: up to 7 cm (2)|
The Barren's topminnow is classified as Endangered (EN) on the IUCN Red List (1).
Discovered as recently as 1982, the Barren’s topminnow is considered to be one of the most endangered fish species in eastern North America (3). Breeding males are striking pale blue-green to yellow-green on the sides of the head and body, and marked with numerous scattered dark red spots. The upperside of the male’s body is olive, with a distinctive white to pale gold stripe running down the midline of the back from the head to the dorsal fin. The dark red spotting extends onto the fins, which are translucent blue, with white and orange bands next to the black fin borders. Females and juveniles are less brightly coloured, with brownish-grey sides marked with numerous dark brown spots, and yellow tinged lower fins (3).
The Barren’s topminnow is found in the US state of Tennessee, where it occurs in the Caney Fork River (part of the Cumberland River drainage) and the Duck, and Elk Rivers (part of the Tennessee River drainage), in the central Barrens Plateau region. In 1984, this species was known from 14 sites, but by 1997 its range had declined to just 2 sites. Fortunately, as a result of reintroductions using captive-bred specimens, the Barren’s topminnow now occurs in several additional sites within its historic range (4).
The Barren’s topminnow inhabits the margins of clear springs and streams, as well as well-vegetated pools (2) (3) (5).
Barren’s topminnow is an opportunistic predator, taking a variety of aquatic invertebrates, such as tiny freshwater crustaceans, midge larvae and snails, along with terrestrial insects that fall into the water or alight on the water surface (2) (3). Spawning takes place in the early spring, when the water temperature reaches 14 to 15 degrees Celsius. The numerous eggs produced by the female adhere to aquatic vegetation, such as fronds of freshwater algae, and are left to hatch unguarded (2) (3) (5). The lifespan of this species is typically two to three years (3).
With an extremely limited distribution, and an accordingly small population, the Barren’s topminnow is particularly vulnerable to extinction from both natural and artificial causes (3). In 1998, a drought at the pool where this species was discovered required the removal of the entire local population. The fish were housed in an artificial facility and re-released after heavy rains replenished the water (5). Along with natural incidents, habitat degradation and development are also significantly affecting this species (3) (5). Perhaps the most severe threat to this species, however, is the introduced non-native western mosquitofish Gambusia affinis (6) (7). Artificially introduced to control mosquitoes by preying on the aquatic larvae, this species has becomes widespread, and has invaded the range of the Barren’s topminnow (7). The invasive species preys on the larval and juvenile stages of Barren’s topminnow, resulting in catastrophic local population declines (6) (8).
Though considered endangered by the state of Tennessee, the Barren’s topminnow does not currently receive Federal protection (3) (5). Fortunately, however, concerted efforts are being made to conserve this imperilled species. In 2001, the Barren’s topminnow Working Group was established, which has been responsible for implementing programmes to restock the Barren’s topminnow at over 24 sites throughout much of its historic range. While many restocking efforts appear to have proven successful, with successful wild breeding occurring, the presence of mosquitofish remains problematic (4). The group is therefore researching and implementing ways to minimise the impacts of the invasive species, including the creation of barriers around one pool occupied by this species to prevent the mosquitofish from entering (4) (5). The group is also undertaking studies to determine the effects of habitat loss and degradation (4). In order to address this threat, it is clear that land management practices encouraging the formation of open water habitats favoured by this species are necessary (3).
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- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.
IUCN Red List (August, 2013)
FishBase (October, 2009)
- Johnson, A.B. and Bettoli, P.W. (2003) Threatened fishes of the world: Fundulus julisia Willams & Etnier, 1982 (Cyprinodontidae). Environmental Biology of Fishes, 68: 240 - .
- Call, G.P. (2008) Cooperative Conservation and Restoration of the Barrens Topminnow (Fundulus julisia) on the Eastern Highland Rim, Tennesee. Natural Areas Revival in Music City: Tuning into a Changing Climate and Biological Invasion, 35th Annual Natural Areas Conference, October 14-17, 2008, Nashville, Tennessee.
Conservation Fisheries (October, 2009)
- Goldsworthy, C.A. and Bettoli, P.W. (2006) Growth, Body Condition, Reproduction and Survival of Stocked Barrens Topminnows, Fundulus julisia (Fundulidae). The American Midland Naturalist, 156: 331 - 343.
- Laha, M. and Mattingly, H.T. (2006) Identifying environmental conditions to promote species coexistence: an example with the native Barrens topminnow and invasive western mosquitofish. Biological Invasions, 8: 719 - 725.
- Laha, M. and Mattingly, H.T. (2007) Ex situ evaluation of impacts of invasive mosquitofish on the imperiled Barrens topminnow. Environmental Biology of Fishes, 78: 1 - 11.