SA Shark Attacks
An analysis of South African shark attack records over the last four decades has shown some interesting patterns.
Most importantly, the results confirm that attacks are rare events, with an average of only six incidents per year. Since 1990 only 26% of attacks have resulted in serious injury and only 15% were fatal. This equates to an average of one serious shark-inflicted injury every year and one shark-inflicted fatality every 1.2 years along some 2000 km of coastline from the Mozambique border to Table Bay (Cape Town).
Initially most attacks took place on swimmers in warm, shallow waters on KwaZulu-Natal beaches, but the shark nets, now concurrently with the drumlines, have greatly reduced the number of these incidents in the province to less than 1 per annum.
There have been only two serious attacks at protected beaches in the last 30 years. Both involved surfers who were bitten in very clear water by a great white shark Carcharodon carcharias. The last attack at a protected beach took place in 1999, which bears testimony to the success of the shark nets in reducing shark attack
Between 2010-2014 the average annual catch was 524 sharks (the bulk of the catch comprising 14 species, 15.7% released alive).Although the KZNSB, through monitoring trends in catch rates of each species, believes that catches of most of the species concerned are sustainable, it is committed to minimising any environmental impact associated with its mandate of protecting sea users from shark attack. Several initiatives have been implemented or are being evaluated in an attempt to reduce mortalities without jeopardising bather safety.
Permanent removal of all nets from selected beaches
The provision of a shark netting service is expensive and historically certain beaches were poorly utilised for a number of reasons. It was therefore decided in 1994 that the cost of providing the netting service at these beaches could not be justified and that all the nets should be removed. Such localities included Tinley Manor and La Mercy to the north of Durban and Ifafa and Mtwalume to the south.
A major initiative has been directed at reducing the number of nets at individual beaches. Logically, given that the nets are fishing devices, fewer nets will catch fewer animals. The initial impetus for this research was provided by a comparison of the KZNSB’s operation with those of its counterparts in New South Wales and Queensland, Australia. In both Australian states, considerably less shark fishing equipment is deployed per protected beach than in KwaZulu-Natal.
Drumlines – an alternative to nets
Another means of reducing environmental impact is the introduction of drumlines in place of some of the remaining nets, such that beaches are protected with a combination of nets and drumlines. A drumline consists of a shark hook suspended from a large anchored float. Drumlines take a reduced catch of harmless animals, compared to a net.
Unfortunately, the shark nets also catch dolphins. The KZNSB has initiated two research projects aimed at determining the efficacy of dolphin deterrent devices in reducing catches. This work has been conducted through generous support from the Endangered Wildlife Trust.
Other options to replace shark nets
The KZNSB has been experimenting with electrical shark repellents for some years.
Electrical Shark Repellent
For over a decade the KZN Sharks Board experimented with the use of electrical fields to repel sharks. In 1996 this culminated in the development and sale of a successful electrical shark repellent, the SharkPOD (Protective Oceanic Device).
The SharkPOD Diver Unit was specifically designed for use by SCUBA divers. Most of the sales were to commercial divers, as recreational divers want to see sharks rather than repel them. The concept was later modified for use by commercial, surface-supply divers, who obtain their air from the surface via an airline.
The SharkPOD Diver Unit consisted of three components linked by cables. The main body of the Diver Unit, housing a small rechargeable 12 V battery pack and one stainless steel electrode, was strapped to the dive cylinder. The foot electrode was attached to one of the diver's fins.
The activating switch, which also housed the low battery warning light, was brought over the shoulder to make it easily accessible. Separated by at least 1.5m, the two electrodes created an electrical field around the diver, which was designed to repel sharks approaching from any direction. This field appeared to affect the shark’s sensory and neuromuscular systems and discouraged the shark from remaining in the immediate vicinity.
The SharkPOD proved effective in scientifically controlled field tests, repelling sharks that came "too close for comfort" (i.e. 1m from the SharkPOD). Most of these tests were conducted on white sharks Carcharodon carcharias on South Africa’s southwest coastline, which is internationally renowned as the best region in which to encounter this species. Tests against the other two species of dangerous sharks which divers are likely to encounter in nearshore waters, namely the tiger Galeocerdo cuvier and the bull (Zambezi) shark Carcharhinus leucas, were limited but with good results. The effectiveness of the device varied according to species, and some harmless sharks, such as the nurse shark Ginglymostoma cirratum, showed little reaction to the electrical field.
The SharkPOD Diver Unit was designed to be activated immediately on entering the water and switched off again only when leaving the water. The device was not intended to be switched on and off during a dive as a startle device - it functioned by keeping sharks at bay. When used correctly, the electrical field was not strong enough to cause undue discomfort to humans.
Distribution of the SharkPOD ended in 2001, but the rights to use the waveform patented by the KZNSB were granted to an Australian company, SeaChange (now called Shark Shield), which now produces repellent devices for use by individuals. Please contact the KZNSB for information regarding suppliers in South Africa.
Shark Repellent Cable
The KZNSB is investigating the possibility of using its patented waveform in a shark repellent cable (SRC) that potentially would surround an entire bathing area with an electrical field. In 2010 the organisation contracted the services of physicists and electrical engineers to assist with this line of research. The project is ongoing.
For information on international shark attack trends, as well as tips on how to avoid a shark attack, please visit the Florida Museum of Natural History website, which is home to the "International Shark Attack File".