Lessons learned from the use of rotenone to eradicate feral fish in two irrigation lakes in Western Australia

Abstract

SummaryAn eradication program using rotenone was implemented primarily targeting a localised population of the feral Pearl Cichlid (Geophagus brasiliensis), and as a secondary objective to also remove the widespread Eastern Gambusia (Gambusia holbrooki) in two artificial lakes used for irrigation purposes in Byford, Western Australia (WA). Rotenone, applied at the approved rate (i.e. 0.25 ppm), failed to eradicate all Eastern Gambusia, and possibly all of the Pearl Cichlids in the first attempt, but at a higher dose rate (i.e. 1 ppm) it eradicated both species on the second attempt. We attributed the initial failure partially to the low dose rate of rotenone approved by the Australian Pesticides and Veterinary Medicines Authority (APVMA). Pearl Cichlids are present in multiple public ponds and lakes, and waterways in the greater Perth metropolitan area (www.abc.net.au/news/2012‐06‐27/feral‐fish‐overtake‐wa‐native‐species/4096580), and needs to be more aggressively managed by the Department of Primary Industries and Regional Development (DPIRD).