Use baited lines instead of nets for shark control
Overall effectiveness category Awaiting assessment
Number of studies: 2
Background information and definitions
Methods of controlling problematic species may have negative impacts on marine and freshwater mammals. For example, shark control nets, which are deployed to protect the public at swimming beaches, may entangle and kill non-target species, such as marine mammals (Gribble et al. 1998). Using alternative methods to capture and remove problematic shark species, such as baited lines, may reduce the risk of marine mammal entanglement and mortality.
Gribble N.A., McPherson G. & Lane B. (1999) Effect of the Queensland Shark Control Program on non-target species: whale, dugong, turtle and dolphin: a review. Marine and Freshwater Research, 49, 645–651.
Supporting evidence from individual studies
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
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