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Surprise Guests in the Pond

What is Swimming in the Lily Ponds?

mosquitofish

Surprise GUESTS

You may have noticed some new swimmers in the pond. These small, brown fish are not guppies; they are mosquitofish. They are related to guppies, but lack the attractive colors of aquarium fish.

We aren’t sure how they got into the ponds. They may have hitched a ride when we relocated the hardy waterlilies to the Jewel Box this Spring.

What is a Mosquitofish?

The western mosquitofish, Gambusia affinis, is naturally found in the southern parts of the United States, including portions of the Mississippi River system. These hardy fish can survive harsh conditions like muddy, low-oxygen waters.

Mosquitofish have a high rate of reproduction, which causes them to eat more, which causes them to reproduce more. Mosquitofish don’t lay eggs like many other fish. They give birth to baby fish – many, many baby fish. This can lead to overwhelming competition with native species and have profound impact on the foot chain of the pond ecosystem.

female mosquitofish
The female Mosquitofish is noticeably larger.
male mosquitofish
Male Mosquitofish

Why are they Called Mosquitofish?

Because of the stagnant, poor water-quality environments, these fish developed a taste for the mosquito larva that also grow there. And boy do they eat eat a lot! People introduced them to non-native waters to help control mosquitos – so the name stuck.

Mosquitofish don’t eat mosquito larva exclusively. They also eat the babies of native fish, other fish, and even amphibians!

Mosquito larva grow in the water, but have to breathe air. They use a snorkel in their tail to take a breath. Mosquitofish patrol the surface looking for them. Image: James Gathany, CDC

IS THIS A BAD THING?

Although we didn’t invite them, they aren’t harming the Jewel Box ponds.

In environments like these concrete lined ponds, mosquitofish provide a valuable service – namely keeping mosquitos in check. In natural habitats where they aren’t native, mosquitofish are considered pests.

Our caretakers are keeping a close eye on these surprise guests to make sure THEY stay in check.

More information on these fish:  Link to Mosquitofish