Action: Brown and black bullheads: Application of a biocide
- A study in the UK reported that use of a piscicide containing rotenone achieved eradication of black bullhead.
- A study in the USA found that rotenone successfully eradicated black bullhead, but one of two ponds required two separate doses.
Biocides may offer a tool for localised eradication or population reduction of bullheads, provided potentially negative effects on native species are carefully managed.
Rotenone has been successfully used to control populations of bullheads and other fish. For example, in the UK, studies have reported that rotenone successfully reduced or eradicated populations of topmouth gudgeon Pseudorasbora parva and fathead minnows Pimephales promelas, from ponds and lakes (Britton et al. 2008; Britton et al. 2011). A risk assessment for piscicidal formulations of rotenone suggests that mortality of bullheads can be achieved with 5-100 parts per billion of rotenone active ingredient, or 100-200 parts per billion of rotenone active ingredient in organic rich ponds, diluted in 38 litres of water, although no scientific evidence was provided (Turner et al. 2007).
It has been suggested that Antimycin is less useful for control of bullheads than rotenone as Antimycin is very toxic to scaled fishes, but is much less toxic to scaleless catfishes (Order Siluriformes), which includes the bullheads (Clearwater et al. 2008).
Britton R., Brazier M., Davies G.D. & Chare S.I. (2008) Case studies on eradicating the Asiatic cyprinid Pseudorasbora parva from fishing lakes in England to prevent their riverine dispersal. Aquatic Conservation: Marine and Freshwater Ecosystems, 18, 867-876.
Britton R., Copp G.H., Brazier M. & Davies G.D. (2011) A modular assessment tool for managing introduced fishes according to risks of species and their populations, and impacts of management actions. Biological Invasions, 13, 2847-2860.
Clearwater S.J., Hickey C.W. & Martin M.L. (2008) Overview of potential piscicides and molluscicides for controlling aquatic pest species in New Zealand. Science for Conservation, 283, 1-74.
Turner L., Jacobson S., & Shoemaker L. (2007) Risk Assessment for Piscicidal Formulations of Rotenone. Compliance Services International, Washington, USA. 104pp.
Supporting evidence from individual studies
A study in 2014 at a fishery in Essex, UK (Environment Agency Invasive Species Action Group 2014) reported that use of a piscicide containing rotenone achieved eradication of black bullhead Ameiurus melas. The piscicide was applied using a boat and a bank based application system. Dead fish were removed using nets. During and after the operation, regular water samples were taken to monitor the level of rotenone.
A study from 2001-2003 in two ponds in Illinois, USA (Towey 2007) found that rotenone successfully eradicated black bullhead Ameiurus melas, but one pond required two separate doses due to an incomplete initial kill. Rotenone was applied in December 2001 using a motorised and hand-pumped sprayer at concentrations of 7 parts per million or 3.5 parts per million, with dose dependent on apparent fish susceptibility. It was applied from several points along banks to ensure complete coverage. A second application was applied in January 2003 as black bullhead catfish were not eliminated in 2001. Ponds were sampled with wire minnow traps, D-frame nets and visual observations to ensure fish had been eliminated.