Introduced fish species
Plague minnows
The plague minnow (Gambusia holbrookii) is a small fish sometimes called the mosquito fish. It was originally introduced to control mosquitoes but was not successful in doing this.
It is now common and widespread, and known to eat native frog eggs and tadpoles. Never introduce this fish into the wild or into a pond in your garden. In some cases, you can remove the plague minnow from a garden pond by draining it and then refilling it once the mud on the bottom has dried.
Other introduced fish species
Other exotic fish - such as trout, carp and goldfish - also eat native frog eggs and tadpoles. These species should not be used to stock garden ponds or dams that are prone to flooding. They should never be released into the wild (although trout can be released into some streams with the approval of relevant authorities).