Fish of the Columbia River


Mosquitofish

Gambusia affinis
Body
Adult length ranges from 0.8 to 2.3 inches (2 to 5.8 cm), with females larger than males. The superior position of the mouth (on top), rounded caudal fin (tail), and large scales on the head are characteristics of the mosquitofish.

Food
The food of the mosquitofish includes a variety of animals, such as zooplankton and small insect larvae, but also includes tiny aquatic plants such as algae and diatoms. The mosquitofish feeds at the water surface and feeding extends to the shoreline in water only an inch deep. The fish get their name because they feed heavily on the larvae of mosquitos. In fact, the species had been introduced in many parts of the United States to control this pest.

Mosquitofish live in quiet, shallow ponds, lakes, ditches, drains, marshes, and sluggish creeks with clear water and plenty or aquatic vegetation. They survive and reproduce best in warm water and tolerate temperatures between 40º and 100ºF (4.5º to 38ºC). They are livebearers (ovoviviparous), which means that the young grow and hatch inside the mother before they are released into the water to fend for themselves.