The effect of introduced western mosquitofish (Gambusia affinis) on ecosystem function in a desert spring

Authors: Steven S. Merkley, Russell R. Rader

Year: 2009 (xli)

Abstract

Western mosquitofish (Gambusia affinis) can be harmful to native fish species because they have physiological, ecological, and behavioral traits that allow them to rapidly reproduce in a wide range of habitats. Previous research in our lab has shown how multiple negative interactions can lead to a decline in least chub (Iotichythys plegethontis), a native cyprinid in the desert springs of western Utah (Mills et al., 2004, Oecologia 141-713-721). Predation on juvenile least chub, similar body size, and competition for space and resources are all factors that have led to the decline of least chub and the proliferation of western mosquitofish in desert springs. We are additionally interested in understanding what impact G. affinis may have on the overall functioning of this spring ecosystem. The objective of this study is to determine the effects of mosquitofish on food webs and ecosystem function in spring ecosystems. We will test the hypothesis that mosquitofish will interrupt the flow of energy from lower (emergent aquatic insects and primary production) to higher trophic levels, and cause a reduction in food available for numerous species that depend on emerging insects (birds, bats, dragonflies, lizards, etc.). Specifically, we expect treatments with invasive mosquitofish to have a direct negative effect on insect emergence and an indirect positive effect on primary production by reducing grazer abundances. Mesocosm experiments will be performed at Fish Springs National Wildlife Refuge, Utah, to determine effects of western mosquitofish on ecosystem function. Ecosystem function will be measured by two response variables: aquatic insect emergence and primary production.