Install barriers at wild fisheries

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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Effectiveness

0%
Certainty

20%
Harms

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Background information and definitions

Barriers may be installed at wild fisheries to deter marine and freshwater mammals from feeding on fish. This may reduce human-wildlife conflict and the motivation to use lethal or harmful deterrents.

Study locations

Key messages

One study evaluated the effects on freshwater mammals of installing a barrier at a wild fishery. The study was in the Puntledge River (Canada).

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (0 STUDIES)

OTHER (1 STUDY)

Human-wildlife conflict (1 study): One randomized, controlled study in the Puntledge River found that installing a ‘cork line’ barrier did not deter harbour seals from feeding on salmon released from a hatchery.

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 1996 at a site in the Puntledge River, British Columbia, Canada (Yurk & Trites 2000) found that installing a ‘cork line’ barrier did not reduce the number of harbour seals Phoca vitulina feeding on migrating juvenile salmon Oncorhynchus spp. under a bridge. Results are not based on assessments of statistical significance. Average numbers of seals feeding on juvenile salmon under the bridge were similar with a ‘cork line’ barrier installed (2–3 seals/30 minutes) and without (2 seals/30 minutes). Seals were observed ‘playing’ with the barrier. In April 1996, a ‘cork line’ (a 60-m rope with cork floats attached at 1 m intervals) was strung across a river below a bridge for an average of 3 h during each of two nights. Juvenile salmon were released from a hatchery. Two observers counted seals feeding on salmon using a red-filtered spotlight every 30 minutes from 2100–0300 h during each of two nights with the barrier and one randomly selected night without.
Study and other actions tested
Referenced paper
Yurk H. & Trites A.W. (2000) Experimental attempts to reduce predation by harbour seals on juvenile out-migrating salmonids. Transactions of the American Fisheries Society, 129, 1360-1366.

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

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Limit the number of fishing vessels or fishing days in an area Action Link	No evidence found (no assessment)	Synopsis Link
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