The Right Fish for the Right Water: How Mosquitofish Fit into Mosquito Control

The Right Fish for the Right Water: How Mosquitofish Fit into Mosquito Control

Rachel B. Bales

Biologist

Your backyard may be home to one of mosquito control’s smallest, and hardest-working, allies.

Summer in Southwest Florida brings afternoon thunderstorms, lush green landscapes, and unfortunately, plenty of mosquitoes. While most people think of mosquito control as trucks making nighttime applications or helicopters treating large areas from above, one of the District’s most effective mosquito control tools spends its entire life underwater.

Meet the mosquitofish.

Despite their modest size, these native fish have been helping control mosquitoes for more than a century (Dill and Cordone, 1997). They provide an environmentally friendly way to reduce mosquito populations, in the correct habitats, and remain an important part of Collier Mosquito Control District’s Integrated Mosquito Management program.

Using Mosquitofish: The How and the Why

Mosquitofish (Gambusia holbrooki) are small, hardy fish native to Florida and much of the southeastern United States. As their name suggests, they have quite an appetite for mosquito larvae that develop in standing water.

When female mosquitoes lay their eggs in standing water, the larvae hatch and spend several days growing near the water’s surface before emerging as adults. This is where mosquitofish come in. They readily feed on mosquito larvae during this aquatic stage, preventing many from ever reaching the flying, biting adult stage.

Their benefits don’t stop there. In addition to feeding on mosquito larvae, mosquitofish can also discourage mosquitoes from laying eggs in the first place. Current evidence suggests that fish release chemical cues into the water that mosquitoes can recognize as an indicator of potential predation (Ritchie and Laidlaw-Bell, 1994; Van Dam et al. 2008; Why and Walton, 2020; Shteindel et al. 2024). Instead of risking the survival of their offspring, female mosquitoes will continue seeking an alternate place to lay their eggs.

Because they reproduce readily and require very little maintenance once established, mosquitofish offer sustainable, long-term biological control in appropriate habitats.

Not a Stand-Alone Solution

Mosquitofish are an effective biological control tool, but they are not a universal solution for mosquito control. Understanding where they work (and where they don’t) is essential.

Mosquitofish can only survive in permanent or semi-permanent bodies of water, such as, small ponds, livestock troughs, retention ponds, certain canals, and persistently flooded ditches. Unfortunately, many of the mosquitoes that cause problems around our homes don’t breed in those places.

Instead, many mosquitoes develop in small natural and artificial containers that collect rainwater, including buckets, flowerpots, bird baths, clogged gutters, children’s toys, old tires, bromeliads, tree holes, and virtually anything capable of holding water for several days. These temporary habitats are ideal for mosquito development but are too small or dry out too quickly to support fish. Other important mosquito species breed in cryptic habitats such as storm drains, catch basins, cisterns, septic systems and waste water treatment features, which are also unsuitable for mosquitofish.

Likewise, large neighborhood lakes, stormwater ponds, and canals are not automatically good candidates for fish stocking. Many of these water bodies already contain fish that feed on mosquito larvae or may already support naturally occurring mosquitofish populations. In addition, fountains, aeration systems, and flowing water create surface disturbance that prevents many mosquito species from laying eggs. Because these water bodies often span multiple properties or entire neighborhoods, they are also frequently too large to stock effectively through the District’s fish program.

It is also important to remember that the mosquitoes biting around a home are not always developing on that property or even within the surrounding neighborhood. In Collier County, several nuisance species, particularly salt marsh mosquitoes, develop in coastal salt marshes and mangrove habitats, including state and federally managed conservation lands. These mosquitoes are strong fliers capable of traveling many miles in search of a blood meal. Additionally, many neighborhoods throughout Collier County border or contain small preserves, cypress swamps, conservation lands, or agricultural areas that also serve as productive mosquito breeding habitats. Mosquitoes emerging from these areas readily disperse into nearby neighborhoods. This means backyard mosquito problems are often unrelated to a resident’s pond, ditch, or other water feature.

Although mosquitofish are native to Florida, they generally should not be manually introduced into natural water bodies, particularly on conservation lands or in other environmentally sensitive areas. Moving fish between water bodies can inadvertently spread invasive species, aquatic pathogens, or parasites and disrupt existing ecological communities. Research has also shown that mosquitofish may consume non-target aquatic organisms (Van Dam & Walton, 2007) and do not always preferentially feed on mosquito larvae when other prey are available (Kumar et al., 2015). For these reasons, the use or movement of mosquitofish should be carefully evaluated within the framework of Integrated Mosquito Management and with consideration for the ecological sensitivity of each site.

This is why mosquito control is most effective when multiple strategies are used together. Biological control with mosquitofish is just one component of an Integrated Mosquito Management (IMM) program that also includes surveillance, source reduction, public education, larval control, and adult mosquito control. No single method can eliminate mosquitoes on its own, but by combining multiple evidence-based strategies, mosquito control programs can provide effective, environmentally responsible protection for public health and quality of life.

Other Ways to Minimize Mosquitoes Around Your Home

Residents also play an important role in mosquito control. One of the most simple and effective ways to reduce domestic mosquitoes is to eliminate standing water around your property.

After heavy rains, take a few minutes to inspect your yard. Empty containers that collect rainwater, clean clogged gutters, refresh bird baths regularly, and remove any unnecessary items that can hold water. Since many mosquitoes can complete their life cycle in less than a week, routinely dumping and draining standing water can prevent hundreds of mosquitoes from developing.

Reducing mosquitoes takes more than just focusing on standing water. During the heat of the day, adult mosquitoes rest in cool, shaded vegetation. Keeping shrubs trimmed and reducing dense, overgrown vegetation around frequently used outdoor spaces can make properties less inviting to adult mosquitoes.

CMCD’s Free Mosquitofish Program

If you have a persistent standing water: full ditch out front, a flooded yard out back, or other water you otherwise wouldn’t dump out: a livestock trough or rain collection barrels, you may already have the perfect home for mosquitofish.

Collier Mosquito Control District provides free mosquitofish to qualifying residents as part of its Mission to protect public health through the suppression of both disease and nuisance mosquito populations. District staff can help determine whether your water feature is appropriate and provide guidance on introducing the fish successfully.

While mosquitofish aren’t the answer for every mosquito problem, they can be a highly effective biological control tool when applied in suitable habitats.

As tiny as they are, these fish make a sizeable impact within our mosquito control program.

For more information about our mosquitofish program or to learn more about the science behind mosquito control, please visit us at www.cmcd.org.

References Cited

Cassiano EJ, Hill JE, Tuckett Q, Watson CA. (2018). Eastern Mosquitofish, Gambusia holbrooki, for Control of Mosquito Larvae: FA202, 4/2018. EDIS, 2018(2). https://doi.org/10.32473/edis-fa202-2018

Dill, William A.; Cordone, Almo J. (1997) History and status of introduced fishes in California, 1871-1996, California Department of Fish and Game Fish Bulletin.178: 1-414.

Kumar R, Muhid P, Dahms HU, Sharma J, Hwang JS. (2015) Biological mosquito control is affected by alternative prey. Zool Stud. 30: 54-55.

Ritchie SA, Laidlaw-Bell C. (1994) Do fish repel oviposition by Aedes taeniorhynchus? J Am Mosq Control Assoc. 10: 380–384.

Shteindel N, Gerchman Y, Silberbush A. (2024) Fish microbiota repel ovipositing mosquitoes. J Anim Ecol. 93: 559-605.

Van Dam AR, Walton WE. (2008) The effect of predatory fish exudates on the ovipostional behaviour of three mosquito species: Culex quinquefasciatus, Aedes aegypti and Culex tarsalis. Med Vet Entomol. 22: 399-404.

Van Dam AR, Walton WE. (2007) Comparison of mosquito control provided by the arroyo chub (Gila orcutti) and the mosquitofish (Gambusia affinis). J Am Mosq Control Assoc. 23: 430-41.

Why AM, Walton WE. (2020) Oviposition Behavior of Culex tarsalis (Diptera: Culicidae) Responding to Semiochemicals Associated with the Western Mosquitofish, Gambusia affinis (Cyprinodontiformes: Poecilliidae). J Med Entomol. 57:343-352.