Plague minnow or mosquito fish? A review of the biology and impacts of introduced Gambusia species

Gambusia affinis and G. holbrooki, introduced worldwide from eastern North America, are collectively the most abundant, widespread freshwater fish in the world, which is not surprising because they tolerate, and sometimes thrive under, an exceptional range of environmental conditions and have high reproductive potential. Some know them as mosquitofish because of a legendary ability to control mosquitoes, and diseases they carry, while others doubt this ability or argue that indigenous fish are equally or more effective. However, rigorous evidence to support these views remains scant, so the legend persists. Some know them as plague minnow because of negative impacts on many native animal species, and abundant evidence exists to support this view. Despite such polarized attitudes toward them, their high abundance and wide distribution, and a large scientific literature devoted to them, many important aspects of their biology remain poorly known.