Topminnow vs. mosquitofish: An update

Authors: Douglas K. Duncan

Year: 2011 (xliii)

Abstract

It has long been known, and thoroughly illustrated in the literature that the western mosquitofish, Gambusia affinis, has major deleterious effects on individual Gila topminnow, Poeciliopsis occidentalis, and their populations. It has been many years since information on this negative impact has been published in the literature. Therefore, I will list and discuss additional examples where mosquitofish have impacted topminnow. In addition, it appears that climate change and long-term drought have a synergistic and negative affect on this relationship. Since the last publications detailing the loss of Gila topminnow populations to mosquitofish, two natural topminnow populations have been lost in the Santa Cruz River basin: Redrock Canyon and Sheehy Spring. Drought and climate change likely assisted mosquitofish with extirpating these two natural populations. Lastly, climate change may facilitate expanded mosquito populations or expanded mosquito seasons within the range of the Gila topminnow. It has also been discussed in the literature that existing tropical and subtropical diseases, or novel diseases, may move north into current Gila topminnow range. If mosquitoes and diseases they carry become more prevalent, the desire and demand for vector control, particularly mosquitofish, will increase. I will discuss tools and programs such as Habitat Conservation Plans and Safe Harbor Agreements that can allow the use of native fish for vector control.