Increase water turbidity to reduce fish predation by birds

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

50%
Certainty

23%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Birds are visual predators and rely on detecting prey within the water in order to hunt. By obscuring predators’ search images overall predation rates might decrease and reduce bird-human conflict in aquaculture operations.

Study locations

Key messages

A randomised trial in France found that little egret Egretta garzetta foraging efficiency was lower in turbid water than clear.

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 randomised trial in southern France found that little egret Egretta garzetta foraging efficiency (capture rate) declined significantly in turbid water, under captive conditions (Cezilly 1992). A 3 x 6 m pool (water depth 10 cm) was used. Nine adult egrets either foraged alone or in threes. Three trials were undertaken using clear or turbid water, with three densities of prey i.e. mosquito fish Gambusia affinis (1, 2, and 4/m²). Treatment order was randomised and trials lasted 5 min. Turbid water was created by adding clay (Secchi disc lost from view at 10 cm depth).
Study and other actions tested
Referenced paper
Cezilly F. (1992) Turbidity as an ecological solution to reduce the impact of fish-eating colonial waterbirds on fish farms. Colonial Waterbirds, 15, 249-252.

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2020) Bird Conservation. Pages 137-281 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

This Action forms part of the Action Synopsis:

Bird Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Spray water to deter birds from ponds Action Link	Unlikely to be beneficial	1	Synopsis Link
Increase water turbidity to reduce fish predation by birds Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Disturb birds at roosts Action Link	Likely to be beneficial	5	Synopsis Link