Words Sarah Titley, pic Jean Tresfon
Human/wildlife conflict is a global problem, with people increasingly competing with animals for space and resources, both in the terrestrial and the marine environment. Cape Town is no exception to this, a buzzing metropolis with a population of 3.74 million people, bordering a national park and surrounded by a marine protected area. In False Bay, negative interactions between great white sharks (Carcharodon carcharias) and people, while extremely rare, have resulted in the necessity for local government to find ways to balance the safety of recreational water users, with the conservation of a globally threatened apex predator.
In 2004, the Shark Spotting programme was started in Muizenberg and Fish Hoek at a community level, to reduce the risk of shark bites by actively monitoring shark activity in the immediate area and alerting people when a shark was present. Adopted by the City of Cape Town in 2006 as its official shark safety strategy, the programme has expanded to cover eight beaches and has recorded over 1500 shark sightings since it started. Periods of high shark activity, coupled with sporadic shark bite incidents, can have far reaching effects for communities, as has been the case at Fish Hoek beach, which in the last 10 years, has had two fatal shark attacks, as well as a third which resulted in severe injuries and the loss of a limb. Due to the high presence of white sharks within the inshore area of the bay, resulting in repeated beach closures, recreational use of Fish Hoek Beach, as well as social perceptions of it, have been negatively impacted. Regular swimmers stopped enjoying the ocean, parents would not bring their children to the beach, lifesavers saw a decline in membership and local businesses suffered, particularly those directly linked to the beach and water activities.
In March 2012, in order to combat these negative effects, and restore public confidence in Fish Hoek beach as a prime recreational node, the City of Cape Town announced it would trial a new method of shark bite mitigation, an exclusion net. Exclusion nets are not the same as traditional shark nets such as those deployed in KZN and Australia. They are small meshed nets, extending from the sea floor to the sea surface, acting as a complete physical barrier to prevent sharks, and other marine animals, from entering a designated exclusion zone. The small mesh of the net prevents capture or entanglement of marine species and the net acts only as a barrier. On the other hand shark nets, like those in KwaZulu Natal, are fishing devices known as large meshed gill nets that entangle, catch and kill sharks, reducing the local shark population and, by fishing for sharks within the vicinity of a protected beach, reducing the risk of shark attack. They cover large geographic areas and are further out at sea than exclusion nets. These nets are not species selective and hence also result in a range of other marine species becoming entangled.
Exclusion nets have been deployed successfully in areas such as Hong Kong and the Seychelles on beaches with very calm conditions and little marine activity. The City of Cape Town faced the challenge of designing a net that would not only be able to withstand the strong sea conditions of the area, but also would have the lowest possible entanglement risk for sharks, cetaceans and other marine life. Following consultation with a number of experts, and an application for a research permit from the Department of Environmental Affairs and the Department of Agriculture, Fisheries and Forestry, the trial began in March 2013 with the design of a net completely unique to any other in the world, in that it would be deployed and retrieved daily, in order to minimise entanglement risk and also the risk of damage from weather conditions or high kelp load. The City extended its contract with Shark Spotters to cover the implementation of the exclusion net trial and provided funding to cover both the capital and operational costs of the project.
The net is made of thick HDPE twine, with a 45 x 45mm mesh. A top rope connected to a series of buoys spaced every 5 metres holds the net at the surface, while two lead weighted ropes keep the bottom of the net on the sea floor. The net is towed out by a rubber duck from the beach in a bunched up “sausage” formation so as to reduce drag and then attached to an anchor point on the catwalk and the beach, as well as a buoy anchored at the deepest part of the net. The boat then travels along the length of the net, unclipping the bunched net and allowing the leaded ropes to pull the bottom of the net down to the sea floor, at which point it forms a complete barrier from sea floor to sea surface.
Shark Spotters trained a group of nine previously unemployed people from a local township, Ocean View, to deploy the net on a daily basis, and also empowered three of the existing spotters to get their skippers tickets to operate the rubber duck. Members of the Shark Spotters and City of Cape Town received training from the Department of Environmental Affairs (DEA), South African Whale Disentanglement Network (SAWDN) and Dolphin Action and Protection Group (DAPG) on how to respond to potential entanglements should they arise, and also developed protocols on what to do should any marine animal approach the exclusion area. The aim of this training was to equip the deployment team with the skills to proactively reduce the risk of entanglement as well as react should an entanglement occur.
An important part of the trial involves the monitoring and research to evaluate the nets effectiveness as a shark safety method, determine whether there are any environmental impacts on the marine life or local environments, determine whether the net affects the trek net fishing in Fish Hoek and evaluate the general use of the area by the public and life-saving club. The monitoring is being conducted by collaboration between Shark Spotters, DEA, Department of Agriculture, Fisheries and Forestry, CSIR, UCT and City of Cape Town.
Preliminary observations from THE FIRST 50 deployments:
• No bycatch
• No entanglements
• Stiff SE - SEE winds and/or strong sea conditions are problematic for deployment and retrieval
• Fish schools seem to be aware of the net and swim alongside it, rather than attempt to get through it
• The presence of whales in the bay have resulted in no or delayed deployment
• Whales have been successfully discouraged following the protocol from moving towards the net once it has been deployed
• There is active uptake by the public with up to 300 people recorded in a single day in the exclusion area
• Fish Hoek life-savers have been using the net for their swim training
The net is deployed during weekends, public holidays and school holidays, weather permitting, and so far has received a good deal of support from the general public. People who haven’t been in the water in Fish Hoek for years are venturing back in the water, parents feel more comfortable allowing their children into deeper water, and the exclusion zone has even become a popular training area for open-water distance swimmers, who were previously confined to training in swimming pools.
The exclusion net will be deployed in Fish Hoek on weekends, public holidays, Tuesday for life-saver training and school holidays from 9am to 5pm, weather permitting. To check if the net is in the water follow Shark Spotters on Facebook and Twitter, where they also post real time shark sightings and beach closures as they happen. www.facebook.com/SharkSpotters @SharkSpotters
Source: The Divesite