Sensitivities of mosquitofish and black mudfish to a piscicide: Could rotenone be used to control mosquitofish in New Zealand wetlands?

Abstract

The comparative sensitivities of mosquitofish (Gambusia affinis) and black mudfish (Neochanna diversus) to the piscicide rotenone were investigated to determine whether it is feasible to use rotenone to control mosquitofish in wetlands inhabited by mudfish. Mosquitofish were exposed to four nominal rotenone concentrations (56, 79, 112, 158 µg.L -1 ) and the time taken for 50% (ET50) and 90% (ET90) of individuals to gasp at the water surface was recorded. Fish were removed from the rotenone at this stage and placed in rotenone-free water to recover. Mudfish were exposed to a single nominal rotenone concentration (100 µg.L -1 ), and removed when hanging at the surface and gulping air. The response time of mosquitofish decreased with concentration. Mean ET50 values were 158 and 26 min for 56 and 158 µg.L -1 rotenone, respectively. Mean ET90 values were 246 and 36 min, respectively. Mudfish were approximately twice as sensitive as mosquitofish to 100 µg.L -1 rotenone. All mudfish recovered following exposure to rotenone. The management implications of the findings are discussed. We suggest that if rotenone were to be used to control mosquitofish in wetlands, it could be applied in summer to remnant standing water as repeated doses of 100-200 µg.L -1 .

A review of rotenone use for the control of non‐indigenous fish in Australian fresh waters, and an attempted eradication of the noxious fish,Phalloceros caudimaculatus

“…A small pilot study conducted during the planning period found that P. caudimaculatus had a high resistance to the chemical (T. Rayner unpubl. data), consistent with results obtained for other poeciliids (Fabacher & Chambers 1972;Willis & Ling 2000). Susceptibility also varies greatly between non-target organisms (Ling 2003).…”

“…Susceptibility of fish species to rotenone is known to vary substantially (e.g., Willis & Ling 2000). Lockett (1998) reviewed several toxicity studies, finding that concentrations of rotenone required to induce death varied widely between species of fish and also between the same species in different studies.…”

“…Since then, rotenone has been used in all Australian states and territories (with the possible exception of Western Australia), with varying success. Although a number of rotenone applications have achieved a complete eradication, many have failed, owing to a wide range of factors that include: the degree of site enclosure (i.e., open versus closed water bodies; Lintermans 2000a); physical water conditions (e.g., temperature, depth, pH, flow velocity; Lintermans & Rutzou 1990b); presence of instream refuges (e.g., dense aquatic vegetation, root masses, undercut banks, ground water recharge); differing susceptibility of target species; rotenone type (i.e., liquid versus powdered rotenone, varying active constituent concentrations; Willis & Ling 2000); and application methods used (e.g., manual, sprayed from ground or air, outboard motor mixing, dripped; Finalyson et al 2000).…”

A Review of the Biology of Gambusia affinis and G. holbrooki

“…Most fish are killed, for example, by a rotenone concentration of about 0.5 ppm, but Gambusia apparently survive this concentration with little mortality (Bonham, 1946). Based on the times taken for 50% and 90% of individuals to gasp at the water surface under different rotenone concentrations, Gambusia is only about half as sensitive to rotenone as Neochanna diversus (Willis and Ling, 2000). Gambusia are more tolerant to ''Dursban'', an organic phosphorus insecticide, than the fish species Lepomis cyanellus and Notemigonus crysoleucas .…”

Toxicity effects of oral gavage of aqueous solutions of cube-root powder and sodium nitrite in common carp

“…One galaxiid species has been tested for its sensitivity to rotenone and was significantly more susceptible than mosquitofish (Willis & Ling 2000). Any eradication project should assess the potential impact on non-target species in order to compare the relative merits of dispersed applications or rotenone baits.…”