The arroyo chub

The arroyo chub (Gila orcutti) is a minnow-like fish native to coastal streams of Southern California. It has a gray-olive green back, white belly, fairly large eyes and a small mouth. Omnivorous, its diet includes algae, insects and crustaceans.

Known to eat immature mosquito populations (larvae and pupae), the Southern California fish is being studied for its mosquito control efficacy. The arroyo chub is a “good candidate to replace the mosquitofish (Gambusia affinis) as a biological control agent for mosquitoes in wetlands where non-native mosquitofish are undesirable; are perceived to pose a threat to native fauna; and where riverine conditions have a negative impact on mosquitofish populations," says UC Riverside entomology professor and entomologist William Walton. He received a grant in June 2006 from the UC Mosquito Research Program to study “The Efficacy of a Native Biological Agent Against West Nile Vectors Inhabiting Constructed Treatment Wetlands.”

The California Department of Fish and Game declared the the arroyo chub "a species of special concern" in 1995. The fish is absent or rare in much of its native range, which includes the Los Angeles, San Gabriel, San Luis Rey, Santa Ana and Santa Margarita rivers and to Malibu and San Juan creeks. Urbanization threatens its habitat, as does introduced minnow species, including the red shiner.

The fish species is named for Charles Russell Orcutt (1864-1929), a San Diego-based pioneer naturalist who first began collecting the fish in 1889. (View his collections from the San Diego Natural History Museum.)

(Photo courtesy of the California Department of Fish and Game)