Mosquitoes

After establishing a new small garden pond, dragonfly larvae and other mosquito predators typically appear by the end of the first summer. Once established, these predators will readily consume any mosquito larvae present. Until the dragonfly populations build up, adding a few fish to the pond can help control mosquitoes. Over time, the pond will generally not need fish for mosquito management. We recommend checking for mosquito larvae occasionally; if larvae are present, introducing a few goldfish can be effective.

Most of our mesocosms (ponds) have goldfish. Some goldfish are brightly colored and easy to spot, while others display the ‘wild-type’ bronze or brown coloration. Native fish would be a wiser ecological choice, but they can be more difficult to obtain and maintain. Goldfish are a non-native invasive species originally from Eurasia, where they inhabit shallow waters such as streams and small ponds. While we typically avoid keeping invasive species, goldfish populations in eastern U.S. freshwater systems have long since stabilized and are now part of the local food web. On our campus, pet goldfish have likely been released into Crim Dell and Lake Matoaka for over a century, and the associated ecological changes are already established. Wild predators, such as barred owls, sometimes visit small garden ponds to feed on goldfish. While this is unfortunate for the goldfish, it supports the broader wildlife community.