Use noise aversive conditioning to deter mammals from fishing gear

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

Effectiveness

20%
Certainty

30%
Harms

10%

Calculating overall effectiveness category

Background information and definitions

Aversive conditioning is the process of associating a negative stimulus with a secondary behaviour or outcome. For this intervention, it involves associating a negative stimulus (a loud startling sound) with a neutral one (a non-startling sound) when marine and freshwater mammals are carrying out undesirable behaviour (predating on fish catches) to the extent that the neutral stimulus alone deters this behaviour. This may reduce the risk of mammals becoming entangled or captured in fishing gear. Mammal predation on fish catches may also decrease, which may reduce human-wildlife conflict at wild fisheries. The study summarised below tested the effects of the first step of this approach only, i.e. pairing a negative stimulus with a neutral one.

Study locations

Key messages

One study evaluated the effects on marine mammals of using noise aversive conditioning to deter mammals from fishing gear. The study was in the North Pacific Ocean (USA).

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (0 STUDIES)

OTHER (1 STUDY)

Human-wildlife conflict (1 study): One study in the North Pacific Ocean found that noise aversive conditioning did not reduce bait foraging behaviour by California sea lions.

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 controlled study in 2013–2014 of five pelagic areas in the North Pacific Ocean, off the coast of California, USA (Schakner et al. 2017) found that attempts to condition California sea lions Zalophus californianus to avoid fishing lines by pairing a ‘startle’ sound with a ‘neutral’ sound did not reduce bait foraging behaviour. Playing ‘startle’ sounds alone reduced sea lion bait foraging behaviour by 83% and sea lions surfaced three times further from fishing vessels compared to when no sounds were played (data reported as statistical model results). However, there was no significant difference in sea lion behaviour when ‘startle’ sounds were played after a ‘neutral’ tone. Commercial passenger fishing vessels carried out fishing stops (each 0.1–2 h) across five areas with sounds played back through an underwater speaker (98 stops) or with no sounds (48 stops). Sounds were either a ‘startle’ pulse (200 ms of white noise at 10–11 kHz) or a ‘startle’ pulse played 2 seconds after a ‘neutral’ tone (6-second tone at 1–2 kHz with a 1.5 second long fade-in). Sound treatments were randomly selected during each fishing stop. Two observers on board each of the fishing vessels recorded bait foraging (sea lions taking bait from fishing lines during at least 50% of the time spent fishing) and distances of surfacing sea lions from vessels during each of the 146 fishing stops in May–September 2013 and 2014.
Study and other actions tested
Referenced paper
Schakner Z.A., Gotz T., Janik V.M. & Blumstein D.T. (2017) Can fear conditioning repel California sea lions from fishing activities? Animal Conservation, 20, 425-432.

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?

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This Action forms part of the Action Synopsis:

Marine and Freshwater Mammal Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Introduce legislation to prohibit or restrict the use of fishing gear types or methods that are harmful to mammals Action Link	No evidence found (no assessment)	0	Synopsis Link
Limit the length of fishing gear in an area Action Link	No evidence found (no assessment)	0	Synopsis Link
Use acoustically reflective fishing gear materials Action Link	Likely to be beneficial	5	Synopsis Link