Electronic Shark Repellent Cable

Testing to commence at Glencairn Beach

  • by onRoute
  • Oct 6, 2014
  • 540
  • News

The KwaZulu-Natal Sharks Board Maritime Centre of Excellence (KZNSB) will commence testing of an electronic shark repellent cable off a Cape Town beach in October. This is a crucial step in the development of technology that one day might provide environmentally friendly alternatives to current shark attack prevention measures.

Announcing the research, KZNSB CEO Mr Mthokozisi Radebe stated: “If this system works, it will keep sharks and bathers at a safe distance from each other without harming either humans or sharks”. He however stressed that as a research experiment the cable will not offer any protection to bathers from sharks as it has been deployed in such a way that will not exclude sharks from approaching Glencairn beach.

The KZNSB has received a permit from the Department of Environmental Affairs (DEA) to test the cable. The cable, 100 metres long, will be installed parallel to the shore at Glencairn beach in early October and will be activated on certain days during daylight hours from the beginning of November until the end of March 2015.

KZNSB CEO Mr Mthokozisi Radebe stated: “If this system works, it will keep sharks and bathers at a safe distance from each other without harming either humans or sharks”.

The cable emits a low frequency pulsed electronic signal, which has been shown to repel white sharks. If successful, it will provide the basis to develop a barrier system that can protect bathers without killing or harming sharks or any other marine animals. It is important to note that this is an experiment and at this time the cable offers no protection against shark attack to bathers or other water users.


The KZNSB has long been investigating the use of new technology to provide alternatives to its current programme of shark nets and drumlines deployed along the KZN coast. The organisation has a legal duty both to protect bathers against shark attack in the province and to minimise the environmental impact of its operations. Technology developed by the KZNSB in the 1990s is already used in the Shark Shield personal shark repellent device that divers and other water users in several countries wear to reduce their risk of shark attack.
A major investment by the KwaZulu-Natal Department of Economic Development, Tourism and Environmental Affairs (DEDTEA) has enabled the KZNSB to undertake further research and development of this technology. In 2012, the Institute for Maritime Technology (IMT), a Division of Armscor SOC Ltd, in Simon’s Town was contracted to design and build a demonstrator cable. The specialist engineering and technical team at IMT first built a short cable that was tested for sea-worthiness. After medical evaluation showed that the electronic pulse emitted was expected to be well within conservative safety limits, a full-length demonstrator cable was constructed.

The system is now ready to be tested in open water. The experiment has the full support of DEA, SanParks, the City of Cape Town, SharkSpotters and other stakeholders.

The Experiment

The system consists of a main cable fixed to the sea floor, with vertical ‘risers’ supporting the electrodes that are fitted on either side of the cable. The risers are semi–rigid and are kept upright by small sub-surface buoys.

Throughout the testing period there will be continuous monitoring of the cable and the area where it is deployed. This will be done by means of a video camera high above the beach and by Shark Spotters who will track the movements of any sharks sighted near the cable. The video footage and the records kept by the Shark Spotters will be analysed by KZNSB scientists to see how the signal emitted by the cable affects white sharks.

The testing period was chosen to coincide with the end of the whale season, to minimise the risk of whale encounters, and the peak white shark season, to maximise the number of possible white shark encounters. Nevertheless the system has been specially adapted for False Bay to prevent whale entanglements by employing semi-rigid risers, not just rope or wires. In addition, a specialised team will be on standby in case a whale does approach the area.

Divers and boat crews from the KZNSB and IMT will monitor and maintain the cable system to ensure it functions as planned. The public may continue to use Glencairn beach as normal while following safety and security precautions to prevent unnecessary contact or interference with the installation, which is deployed beyond the surf break well away from most beach swimmers on the eastern side.

Glencairn Beach

Initially Fish Hoek beach was identified as the ideal location for the experiment but due to possible interference with Trek Net activities, Glencairn beach was chosen as the alternative. White sharks occur naturally in the inshore area off Cape Town during the summer months and this, along with the high-elevation monitoring points, water quality and visibility, and close proximity to IMT, make Glencairn beach a suitable location for the experiment.

The research will in no way impact on the public recreational use of the beach and beach users may continue to use Glencairn beach as normal.

Prior to installation and activation of the system, signage will be installed to provide the public with information on the cable as well as contact numbers for officials in the event of any concerns.

The City of Cape Town will provide on-going support throughout the project. Mayoral Committee Member for Energy, Environmental and Spatial Planning, Councillor Johan Van Der Merwe said: “This is another exciting innovation during the World Design Capital 2014 year that has a global appeal and interest, and the City is excited at the possibilities that lie ahead.”

Questions and answers

Q. Is this shark repellent cable safe for humans?

The electronic shark repellent cable has been subjected to extensive safety evaluation by a medical and scientific team. The same form of pulsed electronic signal has been used within personal shark diver protection devices for many years. The pulse from these devices has been at higher intensities than those expected in the cable, without any reported events.

The safety evaluation has included a review of known relevant research and literature. It has also involved direct research on certain aspects of the field’s effects. The International Electrotechnical Commission refers to a minimum charge expected to cause risk of Ventricular Fibrillation of the heart (the main life-threatening effect of shock) as being of the order of 20 000 micro Coulombs. The cable system is calculated to deliver less than 200 micro Coulombs even with direct contact. Simply put, it would be expected that 100 times the charge produced by the cable would be needed to cause a life-threatening shock. Accordingly, the evidence currently to hand suggests a high level of safety for the average member of the public and even direct contact is unlikely to cause harm. Users of pacemakers are advised to maintain a five-metre distance from the installation due to possible problematic interference in certain unusual subgroups.

Q. What will happen if a person touches the cable?

A. The main cable will be on the sea floor in water six metres deep but if anyone touched it nothing would happen as the cable itself is insulated. There are vertical electrodes (‘risers’) emerging from the cable and if someone touched the small part of an electrode that is exposed, they might experience a tingling sensation.

Q. How close can a person approach the cable?

It is recommended that people stay at least five metres away from the cable to avoid unintentional contact and obstruction of the experiment.

Q. Has anyone been injured by this technology?

A. No. This technology has been used for many years in personal shark repellent devices. The Shark Shield device that uses this technology developed by the Sharks Board is commercially available. It has been shown to be safe in a series of tests and the research team is not aware of any reports of injury related to its use.

Q. Will people be safe from shark attack at Glencairn beach?

No. This is a research experiment. The cable has not been deployed in such a way that it will exclude any sharks from approaching Glencairn beach. Only when all the data from the testing has been reviewed and analysed will it be possible to say whether such a system can be used for bather protection.

Q. What effect will the cable have on white sharks?

The purpose of the testing is to find out how the pulse or signal emitted from the cable acts as a barrier to white sharks. These sharks are highly sensitive to electromagnetic fields. If a shark experiences any discomfort it is able to move away from the cable.

Q. What effect will the cable have on other marine life?

A. No effects have been observed on any other mobile marine animals exposed to the signal, particularly fish and seals.

Q. Will this installation pose a threat to whales?

A. The cable has been specifically designed to minimise the likelihood of a whale becoming entangled. There are likely to still be a few whales in the vicinity at the start of the experiment. Should any whale approach the cable it will be switched off. An inflatable boat stationed at Fish Hoek beach will be deployed to herd the whale from the location. Mr. Mike Meyer, Chairman of the SA Whale Disentanglement Network, will be kept informed and updated about any whale and its behaviour in the Glencairn area.

Q. How does the cable work?

The cable emits a low-frequency, low-power electronic field into the immediate area around the cable, which has been proved to repel white sharks.

Q. How is this system different from other barriers that have been tested?

This system uses an active low-power pulsed electronic field in sea water. It does not use magnets and it does not provide a physical barrier to sharks or other marine animals.

Q. Will bait or other methods of attracting sharks to the area be used?

Nothing will be done to attract sharks to the area. Chumming and all other means of attracting sharks are strictly prohibited by the DEA in terms of the permit allowing this research and would not be supported by the City of Cape Town. The purpose of the experiment is to see how the signal from the cable affects white sharks in their natural environment.

Q. Why is the KZNSB doing research in the Western Cape?

The demonstrator cable that IMT has built is designed to repel white sharks, which are most commonly found in the waters off the Western Cape. These sharks, unlike Zambezi (bull) and tiger sharks, often swim at the surface in daylight hours, so it is far easier to monitor their movements and responses to the cable/barrier. If these tests are successful, further research will need to be conducted against other species and in different conditions.

Q. Will this installation damage the environment?

The system does not include any permanent fixtures or any alterations to the sea floor, beach or shore. All equipment will be removed from the site at the conclusion of the research.

Q. Why was Glencairn chosen?

The area lends itself to testing of this nature due to the high frequency of shark sightings in the area in shark season and the high ground that Elsie’s Peak provides for surveillance purposes. It is also close to the IMT offices in Simon’s Town.

Q. Will this cable be visible from the beach?

All that will be visible is two parallel rows of small floats at the surface that are used to support the risers attached to the cable.

Q. Will the beach stay open?

The beach will remain open to the public throughout the research period.

Q. Is the beach going to be crowded with researchers and equipment?

There will be a presence of KZNSB, IMT and other personnel in the vicinity during the installation period. No equipment will be left on the beach. Visits for monitoring and maintenance are not expected to interfere with normal beach use.

Q. Will the installation interfere with fishing boats or recreational craft?

Such vessels are advised to stay clear in case it presents a hazard. Indicator buoys will be positioned at either end of the array clearly marking the cable start and end. Note that due to tidal variation the risers will not always visible from the surface. All boating clubs and the Simon’s Town harbour master will be notified of the installation’s position at sea.

Q What will happen if swimmers or surfers go over the cable?

The cable has deliberately been deployed outside the surf zone to minimise the chances of such a contact. However, the field should not be felt or cause any harm to swimmers or surfers. Windsurfers, kite-boarders and kayakers will be able to move over the experimental area, but are requested to keep out of the immediate vicinity of the cable to avoid entanglement with the marker buoys.

Q. Will the video camera be filming people using the beach?

The camera view is fixed on the test site, which is a rectangular section of ocean covering the location of the cable and the near field area where sharks are known to occur. The area does not include the beach. Surfers, swimmers or divers and small craft that move close to the cable will be visible. However, the recordings made will only be viewed by the research team for purposes of monitoring shark movements.

Q. Why was IMT chosen to build the cable?

IMT has been doing underwater research and development work for many years and has built up expertise and experience in developing underwater sensors and electronic units. IMT has a huge amount of knowledge about the ocean and its behaviour as well as working in this harsh environment. IMT has also been involved with research and development on underwater sensors (including E Field) as well as various other underwater electronic subsystems. This experience is in line with the development of the Electronic Shark Repellent Cable concept.

For more information, please contact the following people:

KwaZulu-Natal Sharks Board Maritime Centre of Excellence:

  • Media liaison: Head of Business Development Mr Harry Mbambo 083 748 7558
  • Shark Repellent Technology: Project Specialist Mr Paul Von Blerk 083 777 9859
  • Research issues: Head of Research Mr Geremy Cliff 083 777 9839

DEA and South African Whale Disentanglement Network:

Mr Mike Meyer 082 578 7617

Institute of Maritime Technology:

Technical aspects of SRC: Mr Claude Ramasami 021 786 8100

City of Cape Town:

Mr Gregg Oelofse 083 940 8143

Shark Spotters:

Research Manager Dr Alison Kock 072 661 9516