Mosquito Fish

Gambusia_affinis_01Limited Supply, please call ahead.


Free for Jackson County residents


Limit 1 fish per foot length of pond or water feature, up to 25


The District maintains two breeding ponds at our Mosquito Lane address to provide mosquito fish for any Jackson County residents that are in need of them. The small fish swim in groups at the surface of the water and feed on mosquito larvae. They are also placed in water troughs, abandoned swimming pools, and ornamental ponds. This biological method of mosquito control is an alternative to the use of pesticides. Typically the District gives out 5,000 to 6,000 fish per year.

General Information and Care

Mosquito Fish feed on mosquito larvae and adults can consume hundreds per day, from 42%–167% of their own body weight. However, they cannot survive on mosquito larvae alone and also consume small insects, plankton, and other insect larvae.

Mosquito fish can survive relatively inhospitable environments, and are resilient to low oxygen concentrations, high salt concentrations (up to twice that of sea water), and temperatures up to 108 °F.

During the winter, mosquito fish move to the bottom of water sources and become inactive, making a reappearance once the temperatures warm in the Spring.

Considerations for Placement

Mosquito fish can thrive in almost any environment, however consideration must be taken into account when placing them in an environment with other fish or natural predators. In particular, it is advised that mosquito fish not be placed in ponds or water features that contain Bass.

Restrictions on Placement

In recognition of the threat to native-species from exotic species, Oregon law (ORS 498.222) regulates where nonnative fish such as mosquito fish (Gambusia affinis) can be released.  The Oregon Department of Fish and Wildlife (ODFW) has set guidelines restricting the stocking of mosquito fish to “aquaria.” “Aquaria” are any tanks, pools, ponds, bowls or other containers intended for and capable of holding or maintaining live fish and from which there is no outfall to any waters of this state (OAR 635-007-0501).  Natural waterways include creeks, streams, sloughs, ponds, lakes and ditches if connected to natural waterways. Therefore, ponds with an outlet or ones located within the floodplain are not an acceptable location for Gambusia use.