Procambarus crayfish control: Trapping combined with encouragement of predators

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

Effectiveness

50%
Certainty

50%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Combinations of management strategies may have additive or even complementary (synergistic) effects. A combination of trapping and removal alongside encouragement of predators has the potential to manage crayfish populations to low population densities.

Key messages

A before-and-after study in Switzerland found that introducing predators, combined with trapping significantly reduced red swamp crayfish populations in a pond. A second replicated, controlled study from Italy demonstrated that trapping and predation in combination was more effective at reducing red swamp crayfish populations than predation alone.

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 before-and-after study conducted between 1997 and 2001 in ponds in Switzerland (Hefti & Stucki 2006) found that the introduction of natural predators in combination with trapping lowered numbers of the red swamp crayfish Procambarus clarkii. Over a period of four years, the number of crayfish fell from 10,000 to 1,000. Approximately 15,000 crayfish were caught in total. Each night, 0.7-3.4 crayfish were caught/trap. From 1997 to 1999, the natural predators, eel Anguilla anguilla, and pike Esox Lucius, were put in the pond along with 7,000 traps.
Study and other actions tested
Referenced paper
Hefti D & Stucki P (2006) Crayfish management for Swiss waters. Bulletin Français de la Pêche et de la Pisciculture, 380-81, 937-950.
A replicated, paired sites study conducted in 2008 in two artificial canals in Italy (Aquiloni et al. 2010) found that trapping was more effective than using a predator, the eel Anguilla anguilla, in controlling red swamp crayfish Procambarus clarkii populations. Transects containing low densities of eel did not effectively reduce red swamp crayfish Procambarus clarkii densities in comparison to transects containing traps. When trapping was suspended for a month, crayfish populations increased, indicating that trapping effectively reduces crayfish population sizes. In each canal, two transects (150 x 3 m) were delimited using 2 mm-mesh wire netting. Crayfish density was estimated by trapping with 6 traps per transect for one week. After one week, 15 adult eels were put in one transect/canal. Trapping continued for two weeks. The sex and length of each trapped crayfish was determined. The number of live crayfish was monitored.
Study and other actions tested
Referenced paper
Aquiloni L, Brusconi S, Cecchinelli E, Tricarico E, Mazza G, Paglianti A & Gherardi F (2010) Biological control of invasive populations of crayfish: the European eel (Anguilla anguilla) as a predator of Procambarus clarkii. Biological Invasions, 12, 3817-3824.

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?

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This Action forms part of the Action Synopsis:

Control of Freshwater Invasive Species

Related Actions

Actions	Effectiveness	Studies	Category
Procambarus crayfish control: Relocate vulnerable crayfish Action Link	No evidence found (no assessment)	0	Synopsis Link
Procambarus crayfish control: Sterilization of males Action Link	Likely to be beneficial	1	Synopsis Link
Procambarus crayfish control: Trapping combined with encouragement of predators Action Link	Likely to be beneficial	2	Synopsis Link