How to Get Rid of Mosquito Fish

Mosquito fish (Gambusia affinis) are named for their usefulness in eating mosquito larvae. They have been introduced around the world in an effort to control mosquitoes, but they are extremely aggressive and eat the eggs and larvae of other fish and amphibians. Mosquito fish grow up to about 2 1/2 in. long. Do not place them in any natural habitat because of their destructive nature and ability to reproduce rapidly. There are two major ways to remove gambusia: drainage and poisoning.

Things You'll Need

• Contact information for the source of the fish
• Fine netting
• Container for the fish
• Piscicide (fish poison)

Instructions

Contact the Source

1. Contact your local insect control agency or vector control district, especially if you received your mosquito fish from this source in the first place.

2. Discuss different methods of getting rid of your mosquito fish with the least impact on the environment. Insect control organizations are experienced in different techniques for removing mosquito fish and can guide you through local regulations regarding removal methods.

3. Get a permit. In most situations, local or state regulations require a permit for fish eradication. Check the regulations in your area before proceeding.

Drain the Water

1. Choose a season when amphibians will be able to aestivate (live without water) for a short time so you don't kill them as well.

2. Net the area where the water will drain. This will keep the fish from entering the environment. For a small water source like a trough or fountain, you can use a small hand net.

3. Cover drainage outlets completely and securely with net fine enough to catch even juvenile mosquito fish. If your pond or containment area can be drained into a space where the fish can't survive (like a field), you do not have to net the fish unless you want to save them.

4. Drain the area. When possible, the best way to get rid of all mosquito fish is to drain the water source completely. Remove the fish from the netting and place in a container if you wish to save them.

5. Leave the area dry for a few days and then refill. Make sure any remaining puddles and depressions do not contain any living mosquito fish before you refill.

Poison the Fish

1. Evaluate what species will be affected if you use a poison. In small ponds containing ornamental fish, it is sometimes easier to remove those fish and then use piscicide (fish poison) to kill the remaining mosquito fish. Be aware that other species of native fish will may be affected by poisoning.

2. Apply a piscicide. Several poisons can be used to remove mosquito fish, but they should only be administered in contained water sources by professionals. Poisons include slaked lime, antimycin and rotenone.

3. Apply a sublethal dose of piscicide to minimize effects on other wildlife. Applying rotenone causes fish to become hypoxic (they can't breathe), so a sub-lethal dose can bring the fish to the surface. As they gulp air to survive, you can net and remove them.

4. Choose a selective poison. Antimycin is used to kill scaled fish and is used for special applications where non-scaled fish like catfish are not targeted.

Tips & Warnings

• Mosquito control agencies across the United States supply mosquito fish on a permit basis. Take special care in choosing whether or not to use mosquito fish in your situation, as these fish have the potential to cause a lot of environmental damage.

• Fish poisons should only be administered under carefully controlled conditions. Always follow manufacturer's instructions for using piscicides and be aware of their possible affects on other wildlife and pets.

• Rotenone and slaked lime are indiscriminate poisons and will kill all species of fish.

References

• Los Angeles County West Vector: Mosquitofish
• Global Invasive Species Database: Gambusia affinis
• Mississippi State University: Using Rotenone to Renovate Fish Populations in Farm Ponds