American bullfrog control: Direct removal of juveniles

Overall effectiveness category Likely to be beneficial
Number of studies: 2
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How is the evidence assessed?

Effectiveness

70%
Certainty

60%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Direct removal of the early lifecycle stage may offer a tool for localised population reduction when used as part of an integrated pest management strategy for controlling invasive bullfrog populations. For example, a replicated field based and modelling study from 1999 to 2003 on Southern Vancouver Island, Canada (Govindarajulu et al. 2005) found that culling bullfrog metamorphs in autumn was the most effective method of decreasing population growth rate.

Govindarajulu P., Altwegg R. & Anholt B.R. (2005) Matrix model investigation of invasive species control: bullfrogs on Vancouver Island. Ecological Applications, 15, 2161–2170.

Key messages

One replicated study in Belgiumfound 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

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
Referenced paper
Louette G, Devisscher S & Adriaens T (2014) Combatting adult invasive American bullfrog Lithobates catesbeianus. . European Journal of Wildlife Research, 60, 703-706.
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
Referenced paper
Guibert S, Dejean T & Hippolyte S (2010) The Regional Natural Park Périgord-Limousin: territory of experimentation and innovation by the implementation of an eradication program of the bullfrog (Lithobates catesbeianus) associated with a research program. EPOPS: La Revue des Naturalistes du Limousin, 79, 15-24.

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

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This Action forms part of the Action Synopsis:

Control of Freshwater Invasive Species

Related Actions

Actions	Effectiveness	Studies	Category
American bullfrog control: Draining ponds and altering the length of time for which the pond contains water Action Link	No evidence found (no assessment)	0	Synopsis Link
American bullfrog control: Biological control of co-occurring beneficial species Action Link	No evidence found (no assessment)	0	Synopsis Link
American bullfrog control: Biological control using native predators Action Link	Likely to be beneficial	1	Synopsis Link