American bullfrog control: Biological control using native predators

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

Key messages

  • One replicated, controlled study conducted in Belgium found the introduction of the northern pike led to a strong decline in bullfrog tadpole numbers.


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. One replicated, controlled study conducted from 2007 to 2009 in Balen, north-eastern Belgium (Louette 2012) found the introduction of the northern pike Esox lucius led to a reduction in bullfrog tadpole biomass with time, which was not significant overall, but highly significant from Spring year two.   In year two, tadpole biomass in ponds with introduced pike reached only a tenth of their biomass in control (unmanaged) treatments in year two.  No effect of draining was observed.  Four treatments were randomly assigned to twelve ponds. The control included two replicates with no draining and no pike. The second treatment included four replicates of pike, but no draining. . The third included three replicates of draining and no introduction of pike. The fourth included three replicates of pike and draining.  Draining was performed in June 2007, with removal of all amphibians and fish.  Juvenile pike were introduced in May 2008 and 2009.

    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

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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.

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