Response of California red-legged frogs to removal of non-native fish

  • Published source details Alvarez J.A., Dunn C. & Zuur A.F. (2002) Response of California red-legged frogs to removal of non-native fish. Transactions of the western section of the Wildlife Society, 38/39, 9-12.


This study is summarised as evidence for the following.

Action Category

Remove or control fish by drying out ponds

Action Link
Amphibian Conservation
  1. Remove or control fish by drying out ponds

    A replicated, before-and-after study in 1998–2003 of seven ponds in California, USA (Alvarez, Dunn & Zuur 2002/2003) found that the reproductive success of California red-legged frogs Rana draytonii increased significantly following elimination of non-native fish by pond drying. Adult numbers were similar after fish elimination (0–40 to 1–41/pond), but juveniles increased significantly (0–15 to 1–650). Fish were eliminated during the first draining, or for two ponds with mosquitofish Gambusia affinis on the second draining. Seven ponds were drained in autumn in 1998–2001. Pumps were used to drain the water to a depth of 50 cm and then below 3 cm. Seines, throw nets and dip nets were used to remove all fish. Mud was smoothed and a small amount of household bleach applied to eliminate mosquitofish. Ponds were filled from ground water springs. Red-legged frogs and fish were surveyed six times per year in 1998–2001.


Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust