Toxicity of the Piscicide Rotenone to Columbia Spotted Frog and Boreal Toad Tadpoles

Abstract

The piscicide rotenone is commonly used to remove nonnative fishes from natural aquatic systems. While the effects of rotenone on fish are well documented, the effects of this chemical on amphibians are less well known. We determined the toxicity of the rotenone formulation CFT Legumine (5% rotenone) to three ages—Gosner age ranges 21–25, 30–35, and 40–45—of tadpoles of the Columbia spotted frog Rana luteiventris and the boreal toad Anaxyrus boreas under laboratory conditions. Tadpoles of both species were exposed to 0.1, 0.5, and 1.0 mg/L CFT Legumine (0.005, 0.025, and 0.050 mg/L rotenone, respectively) in static, 96‐h exposure trials; surviving individuals were placed in rotenone‐free water and raised until metamorphosis. In an additional experiment, Columbia spotted frog tadpoles were exposed to 1.0 mg/L CFT Legumine for 1, 2, 3, or 4 h before being placed in rotenone‐free water for the duration of a 96‐h exposure period. Tadpole mortality increased with increases in CFT Legumine concentration and exposure period. Individuals exposed to 1.0 mg/L of product experienced significantly greater mortality than did control tadpoles (P < 0.001), with 99–100% mortality occurring in the youngest age‐group (Gosner 21–25) in both species. In Columbia spotted frog tadpoles, mortality decreased as age increased, while age did not affect mortality in boreal toad tadpoles. Rotenone produced no biologically significant effects on growth or metamorphosis. Our findings suggest that the use of 1.0 mg/L CFT Legumine to remove nonnative fish may cause significant mortality to larval amphibians if they are exposed for 96 h; exposures to lower dosages (0.5 mg/L of product) or for shorter durations (≤4 h), however, resulted in less mortality. Fisheries managers can use these results to improve amphibian conservation in fish restoration areas and reduce the impacts on larval amphibian populations.

Effects of Rotenone on Columbia Spotted Frogs Rana luteiventris during Field Applications in Lentic Habitats of Southwestern Montana

“…Somewhat contradictory to our field observations, the laboratory studies of Billman et al (2011) found low mortality (6%) in Gosner stage 44-45 Columbia spotted frog tadpoles exposed to CFT Legumine at 1 mg/L. However, there may be a plausible explanation for this discrepancy.…”

“…The introduction of rotenone can have immediate, negative impacts on nontarget, gill-breathing aquatic organisms, such as amphibians (Fontenot et al 1994;McCoid and Bettoli 1996;Maxell 2000;Patla 2005). Laboratory studies have demonstrated that CFT Legumine (5% rotenone) can cause significant mortality in boreal toad Anaxyrus boreas and Columbia spotted frog Rana luteiventris tadpoles at dosages commonly used in field applications (Billman et al 2011). Similarly, Grisak et al (2007b) documented mortality in a variety of native Montana amphibian larvae after exposure to rotenone products.…”

“…To maintain and preserve extant populations of amphibians during fish eradication projects, it is important to measure the effects of rotenone under field conditions, thereby building upon knowledge gained from recent laboratory experiments on amphibians (Grisak et al 2007b;Billman et al 2011). The overall goal of this research was to document some of the short-and longer-term impacts of rotenone exposure on amphibians in a field setting.…”

Application of environmental DNA analysis to inform invasive fish eradication operations

“…Attempts to eradicate non-native fish species often involve application of a piscicide, such as rotenone (Allen et al 2006; Britton et al 2008), even though this practice can have substantial impacts on non-target fauna (e.g. Finlayson et al 2010; Billman et al 2011). In some circumstances, such as isolated water bodies, it may be possible to eradicate a fish species through a drain-down and liming of the water body (Britton et al 2008).…”

Analysis of active rotenone concentration during treatment of the Rondegat River, Cape Floristic Region, South Africa

“…Besides having a strong piscicidal effect, in the aquatic environment rotenone poses a risk to a variety of gill-respiring organisms including tadpoles and macroinvertebrates (Blakely et al 2005;Finlayson et al 2009;Billman et al 2011). Rotenone is a very unstable compound and degrades by a variety of mechanisms including hydrolysis (t ½ -values vary from 2.0 d at pH 9 to 12.6 d at pH 5 [Thomas 1983]), photolysis (t ½  1.4 h [Spare 1982] to 8.2 h [Draper 2002]), and is metabolised by bacteria (Spare 1982), fish (Gingerich andRach 1985) and mammals (Eiseman 1984).…”