Using a California native fish as an alternative biocontrol agent to the mosquitofish (Gambusia affinis), a case study

Arroyo chub, Gila orcuttii, a fish endemic to Southern California watersheds, has been proposed as a replacement biological control agent for the invasive Western mosquitofish, Gambusia affinis, in sensitive watersheds throughout southern California. Survival and efficacy of the chub at controlling larval mosquitoes, specifically Culex tarsalis, the Western encephalitis mosquito, was evaluated at the Prado Wetlands in Orange County, California. Mosquito-eating fish are not strictly larvivorous in their diets and have the potential to impact non-target organisms, leading to trophic shifts in systems where they are introduced. We studied the impact of predation by the chub on the aquatic community that co-occurs with larval mosquito populations, specifically the macroinvertebrate and planktonic communities. The chub has been designated as a “Species of Special Concern” by Cal. Dept. of Fish and Game and the long-term goal is to provide Vector Control Districts with a native alternative to Gambusia, while helping to enhance the chub population and return the fish to its native range.