Replace or repair damaged anti-predator nets around aquaculture systems

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

Effectiveness

50%
Certainty

28%
Harms

10%

Calculating overall effectiveness category

Background information and definitions

Anti-predator nets may be placed around fish pens and cages to physically exclude marine or freshwater mammals to reduce predation and human-wildlife conflict. However, such nets may entangle mammals causing injury or death. Frequently replacing or repairing anti-predator nets may reduce the risk of mammals becoming entangled within holes or loose sections of damaged nets (Kemper et al. 2003). This may also prevent mammals from breaching the nets thereby reducing human-wildlife conflict.

For studies that involve modifying anti-predator nets, see Modify anti-predator nets around aquaculture systems.

Kemper C.M., Pemberton D., Cawthorn M., Heinrich S., Mann J., Würsig B., Shaughnessy P. & Gales R. (2003) Aquaculture and marine mammals: Co-existence or conflict? Pages 208–224 in: N. Gales, M. Hindell & R. Kirkwood (eds.) Marine mammals: Fisheries, tourism and management issues. CSIRO Publishing, Collingwood, Victoria, Australia.

Study locations

Key messages

One study evaluated the effects on marine mammals of replacing anti-predator nets around aquaculture systems. The study was in the North Atlantic Ocean (USA).

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (0 STUDIES)

OTHER (1 STUDY)

Human-wildlife conflict (1 study): One site comparison study in the North Atlantic Ocean found that replacing anti-predator nets more frequently at salmon farms resulted in fewer salmon losses to harbour seal predation.

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 site comparison study in 2001–2003 of 26 Atlantic salmon Salmo salar farms in the western North Atlantic Ocean, off the coast of Maine, USA (Nelson et al. 2006) found that farms that replaced anti-predator nets more frequently had fewer fish losses to Western Atlantic harbour seal Phoca vitulina concolor predation than those that replaced nets less frequently. Farms that replaced anti-predator nets more than once/year reported fewer losses of fish to seal predation than farms that replaced anti-predator nets once/year or less (data reported as statistical model results). Twenty-two farms replaced anti-predator nets more than once/year. Four farms replaced nets once/year or less. Farm managers were sent annual questionnaires in 2001–2003. Data were collected on methods used to deter predators and estimated numbers of fish lost or damaged due to seal predation.
Study and other actions tested
Referenced paper
Nelson M.L., Gilbert J.R., Kevin J. & Boyle K.J. (2006) The influence of siting and deterrence methods on seal predation at Atlantic salmon (Salmo salar) farms in Maine, 2001–2003. Canadian Journal of Fisheries and Aquatic Sciences, 63, 1710-1721.

Please cite as:

Berthinussen, A., Smith, R.K. and Sutherland, W.J. (2021) Marine and Freshwater Mammal Conservation: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, 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:

Marine and Freshwater Mammal Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Introduce and enforce legislation to prevent intentional killing of mammals at aquaculture systems Action Link	No evidence found (no assessment)	0	Synopsis Link
Translocate mammals away from aquaculture systems to reduce human-wildlife conflict Action Link	Likely to be ineffective or harmful	2	Synopsis Link
Use acoustic devices at aquaculture systems Action Link	Trade-off between benefit and harms	6	Synopsis Link