American bullfrog control: Direct removal of juveniles

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Key messages

  • One replicated study in Belgium found double fyke nets were effective in catching bullfrog tadpoles in small shallow ponds.
  • One before-and-after study in France found a significant reduction in the number of recorded adults and juveniles following the removal of juveniles by trapping, when carried out as part of a combination treatment.


About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated study in 2010 and 2011 across three sites in Belgium (Louette et al. 2014) found catchability of bullfrog tadpoles in small shallow ponds using one double fyke net for 24 h to be reasonably consistent at approximately 6%.  Bullfrog populations were investigated in ten permanently wet, small, shallow fish ponds (average surface area 1,500 m2; max depth 150 cm), across three sites.  In six water bodies (Hoogstraten and Arendonk), bullfrog tadpole population density was estimated.  In these ponds, a number of double fyke nets were set (parallel and two meters out from the shore) for 24 h, covering all sides of the water body. A minimum of three catch efforts of equal magnitude were performed. After every catch effort, all captured individuals were removed from the population.   To determine the accuracy of these population size estimates, calibration using seine netting was performed in two ponds.

    Study and other actions tested
  2. A before-and-after study from 2006 to 2009 on Natural Park Périgord-Limousin sites in France (Guibert et al. 2010) found a significant reduction in the number of recorded adults and juveniles following the removal of juveniles by trapping, along with other removal methods.  The number of trapped tadpoles decreased from approximately 1,600 in 2006 to fewer than 200 in 2009.  Trapping was carried out as part of a combination treatment which also involved shooting of adults and collection of egg clutches.  Unbaited single and double entry traps were installed equidistant from each other in the water, and were checked daily until the catch rate became negligible compared to the work effort.

    Study and other actions tested
Please cite as:

Aldridge, D., Ockendon, N., Rocha, R., Smith, R.K. & Sutherland, W.J. (2020) Some Aspects of Control of Freshwater Invasive Species. Pages 555-87 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Control of Freshwater Invasive Species

This Action forms part of the Action Synopsis:

Control of Freshwater Invasive Species
Control of Freshwater Invasive Species

Control of Freshwater Invasive Species - Published 2017

Control of Freshwater Invasive Species Synopsis

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