Mosquito Fish – Gambusia holbrooki

The mosquito fish (Gambusia holbrooki) originates from the southern United States and has spread extensively to many countries around the world as a result of its initial use as a biological agent to control mosquitoes.

Gambusia holbrooki

© Photo : Daniel Garcia -

Although it is no longer considered to be a more effective mosquito-control agent than other native fish species, it is known to be used as a feeder for some aquarium-fish species.

This small, aggressive fish can be found in many habitats but thrives best in warmer, slow flowing water where the surface vegetation is not excessively dense.

The key environmental concern is that, once it becomes established, it preys on amphibians and native fish and competes aggressively for food, thus resulting in extensive damage to the native habitat and aquatic populations.

The main pathways of spread of the mosquito fish are through release or disposal of water garden fish into creeks and waterways and by attachment to plumage of wading birds. There are no known effective, long-term control measures available once these fish invade a habitat.

Prevention of accidental release remains the most effective method of controlling their spread. This can be achieved by not disposing of unwanted water garden fish into native waterways, or by returning or donating unwanted fish to a school, another hobbyist or local organization that can provide a home or find a new owner.

For more detailed information on this invasive aquatic animal, contact:

Global Invasive Species Database;

Ontario Federation of Anglers & Hunters;

Ontario's Invading Species Awareness Program.