C.A. Goldsworthy | Geology Reports

USGS2011

Larval fish dynamics in spring pools in middle Tennessee

We used lighted larval traps to assess reproduction by fishes inhabiting nine spring pools in the Barrens Plateau region of middle Tennessee between May and September 2004. The traps ( n = 162 deployments) captured the larval or juvenile forms of Etheostoma crossopterum (Fringed Darter) ( n = 188), Gambusia affinis (Western Mosquitofish) ( n = 139), Hemitremia flammea (Flame Chub) ( n = 55), the imperiled Fundulus julisia (Barrens Topminnow) ( n = 10), and Forbesichthys agassizii (Spring Cavefish) ( n = 1). The larval forms of four other species (Families Centrarchidae, Cyprinidae, and Cottidae) were not collected, despite the presence of adults. Larval Barrens Topminnow hatched over a protracted period (early June through late September); in contrast, hatching intervals were much shorter for Fringed Darter (mid-May through early June). Flame Chub hatching began before our first samples in early May and concluded by late-May. Juvenile Western Mosquitofish were collected between early June and late August. Our sampling revealed that at least two species (Flame Chub and Fringed Darter) were able to reproduce and recruit in habitats harboring the invasive Western Mosquitofish, while Barrens Topminnow could not.

Southeastern Naturalist↗

USGS2006

Growth, body condition, reproduction and survival of stocked barrens topminnows, Fundulus julisia (Fundulidae)

We documented the fate of 29 cohorts of propagated Barrens topminnows Fundulus julisia stocked as juveniles and adults (ntotal = 2770 fish) into 17 springheads and small ponds in middle Tennessee in 2003 and 2004. Annual mortality rates were calculated after estimating the number of individuals of each cohort remaining 1-18 mos after fish were stocked. Lighted larval fish traps were deployed at seven reintroduction sites and the Type Locale to determine whether topminnows could reproduce in the presence of the introduced-transplanted Western mosquitofish Gambusia affinis. At stocking sites harboring mosquitofish (n = 12), their density ranged from 0.4 to 66.3 mosquitofish per m2. Annual mortality of stocked Barrens topminnows ranged from 45 to 100% and 24 cohorts experienced annual mortality greater than 95%. Mortality was not related to mosquitofish density or the mean size at stocking. The robustness of Barrens topminnows did not differ in the presence or absence of mosquitofish, suggesting that interspecific competition for food was not occurring. Larval Barrens topminnows were collected at two reintroduction sites and the Type Locale, but juvenile recruits were produced only at sites lacking mosquitofish. The findings of this study, and concurrent laboratory studies, support the hypothesis that mosquitofish predation on larval Barrens topminnows was the primary mechanism in failed reintroductions and is the greatest threat to wild and reintroduced populations of this imperiled species.

American Midland Naturalist↗