WDFW LogoWashington Department of Fish & Wildlife
WDFW LogoConservation

To report an AIS
sighting or to find out
more information call

Questions or comments regarding the state's Aquatic Invasive Species and Ballast Water Management Programs may be directed to:

Allen Pleus
AIS Coordinator
(360) 902-2724

View WAC 220-12-090
Classification - Nonnative aquatic
animal species with photos

Gambusia affinis (Mosquito fish)

Animal Fish
Family: Poecilidae
Classification: Regulated

Mosquito Fish
Mosquito fish

The virtues of the mosquito fish, Gambusia affinis, have been extolled by many mosquito control organizations. However, the species can be a major pest when introduced outside their natural range. In addition to eating mosquito larvae they eat a variety of other insect larvae, zooplankton and aquatic plants. They are aggressive and have been known to feed on eggs, larvae, and juveniles of various native fishes and amphibians. Because of these negative impacts, Gambusia is a regulated species in Washington State, and cannot be introduced without a fish stocking permit. Under current WDFW policy, transfer/stocking permits may only be issued to organized Mosquito Control Districts, the U.S. Army Corps of Engineers, and city, county or state health departments, they may not be issued to private individuals. It is prohibited to stock Gambusia in Clallam, Jefferson, Kitsap, Grays Harbor, Mason and Thurston and portions of Lewis County that drain into the Chehalis river to protect the Olympic mud minnow.