Toxicity effects of oral gavage of aqueous solutions of cube-root powder and sodium nitrite in common carp.
Context. Common carp (Cyprinus carpio) is a highly invasive freshwater pest fish that has been linked to waterway degradation when it has been introduced and exists at high densities. The deployment of a toxic bait may be a logistically simple tool that wildlife managers could use to reduce carp populations. Rotenone, the piscicide most commonly used in previous attempts to produce a carp bait is very expensive, albeit highly toxic to carp. We investigated the toxicity of two potential alternative piscicides to carp. Aim. To determine the oral toxicity of two alternative cheaper toxins to carp, cube-root powder (CRP) and sodium nitrite (nitrite). Methods. CRP or nitrite was administered in an aqueous solution by gavage to lightly sedated captive carp. The aqueous solution consisted of a 30:70 mixture (w/w) of the surfactant, Polysorbate 80, to increase the absorption of toxins through the intestine, and water. Key results. The LD50 of CRP and nitrite in carp was 135.7 mg kg-1 and 122.0 mg kg-1, respectively. Conclusions. Both CRP and nitrite are toxic to carp at dose rates low enough to be incorporated into a piscicide bait for this species. Implications. Both CRP and nitrite appear to be viable alternative oral piscicides to rotenone for carp and warrant further investigation of delivery in bait.