Life History and Ecology of the Barrens Topminnow, Fundulus julisia Williams and Etnier (Pisces, Fundulidae)

The life history of the Barrens topminnow, Fundulus julisia, was investigated in a two-year study from 1983 to 1985. The species is restricted to a few isolated springs and groundwater-influenced upland streams on the Barrens Plateau in the vicinity of Manchester in middle Tennessee. In most aspects of its behavior, including feeding and reproduction, this topminnow differs little from other members of the same genus. The fish is an opportunistic carnivore, feeding upon aquatic insects, crustaceans, and gastropods, as well as terrestrial insects that fall in water. Like other killifish, F. julisia has an extended breeding season that is bimodal with peaks in the last spring and late summer. The requirement of filamentous algae and/or other aquatic plants for a spawning site and the paucity of permanent upland waters supporting their growth is apparently the primary factor limiting the species to its currently restricted distribution. F. julisia has a maximum lifespan of about three years, but mortality is high among adults following reproduction and relatively few survive to spawn more than once. Mortality is higher in males than in females older than one year, presumably due to selective predation upon the more brightly colored males. Growth in the first year is very rapid when compared to other Fundulus. Possible predators of young Barrens topminnows are numerous, but piscivorous wading birds are probably the primary predators of adults. A potentially serious threat to all Barrens topminnow populations is Gambusia affinis which bears live young continuously throughout the warmer months and tends to grossly outnumber topminnows where the two are syntopic. The mosquitofish has been known to replace native species elsewhere. Droughts of the past few years as well as habitat alterations by man, especially those affecting groundwater levels, also may endanger the species' survival.