Use baited lines instead of nets for shark control

How is the evidence assessed?
  • Effectiveness
    70%
  • Certainty
    50%
  • Harms
    10%

Study locations

Key messages

  • Two studies evaluated the effects on marine mammals of using baited lines instead of nets for shark control. One study was in the Indian Ocean (South Africa) and one in the South Pacific Ocean (Australia).

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

  • Survival (1 study): One site comparison study in the South Pacific Ocean found that using baited lines instead of nets increased the survival of entangled common and bottlenose dolphins.

BEHAVIOUR (0 STUDIES)

OTHER (2 STUDIES)

  • Reduction in entanglements/unwanted catch (2 studies): Two site comparison studies in the Indian Ocean and South Pacific Ocean found that baited lines used for shark control had fewer entanglements of dolphins, whales and dugongs than nets.

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

  1. A site comparison study in 2007–2010 at 17 coastal sites in the Indian Ocean, South Africa (Cliff & Dudley 2011) reported that baited lines used for shark control had fewer entanglements of dolphins and whales than nets. No whales or dolphins were found entangled in baited lines, whereas an average of seven dolphins and two whales (species not reported) were found entangled each year in nets. Catch rates and survival of target sharks on baited lines and in nets differed between species (see original paper for details). In 2007, half of the shark-control nets (214 m long x 6 m deep; number not reported) previously deployed to protect 17 beaches were replaced with 76 baited ‘drum’ lines (single lines suspended beneath a float with a baited ‘J hook’). The nets and lines were checked 18 times/month in 2007–2010.

    Study and other actions tested
  2. A site comparison study in 1992–2008 at three coastal sites in the South Pacific Ocean, Queensland, Australia (Sumpton et al. 2011) found that baited lines used for shark control had fewer entanglements of four dolphin species, humpback whales Megaptera novaeangliae and dugongs Dugong dugon than nets, and survival of entangled dolphins was higher on baited lines.  Overall, baited lines had fewer entanglements than nets of common dolphins Delphinus delphis (5 vs 74 respectively), bottlenose dolphins Tursiops spp. (6 vs 26), Indo-Pacific humpback dolphins Sousa chinensis (0 vs 12), spinner dolphins Stenella longirostris (0 vs 12), humpback whales (0 vs 26) and dugongs (0 vs 9). Survival of entangled common and bottlenose dolphins was higher on baited lines (both 100%) than in nets (common: 5%; bottlenose: 8%). Catch rates and survival of target sharks on baited lines and in nets differed between species (see original paper for details). At each of three locations, 9–35 baited ‘drum’ lines (single lines suspended beneath a buoy with a baited shark hook) and 3–11 shark-control nets (186 m long x 6 m deep, 50 cm stretched mesh size) were deployed to protect beaches. All lines and nets were deployed parallel to the shore in water 6–12 m deep. Fishers checked and re-baited the 56 lines and 17 nets during 15–20 days/month in 1992–2008.

    Study and other actions tested
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

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Marine and Freshwater Mammal Conservation

This Action forms part of the Action Synopsis:

Marine and Freshwater Mammal Conservation
Marine and Freshwater Mammal Conservation

Marine and Freshwater Mammal Conservation - Published 2021

Marine and Freshwater Mammal Synopsis

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