Research at the KZN Sharks Board
The KZNSB is one of the world’s leading shark research organisations. The Research Division conducts and facilitates various scientific activities, which include monitoring, documenting and dissecting all catches, collecting biological samples, investigating shark attacks and investigating new non-lethal alternatives to the current shark safety gear. The research results address the organisation’s legislated mandate in terms of (i) bather protection, (ii) recording of catches, (iii) reduction in environmental impact and (iv) biological research. The division provides technical and scientific knowledge that is passed on to the community both locally and internationally.
The Division provides scientific support to the Operations Division, assisting it in reducing negative environmental impacts through promoting tag-and-release of live sharks, reducing nets, replacing some nets with drumlines and deploying marine mammal deterrents. Currently, an important focus of research is the development of an electrical shark-repellent cable (SRC) which, it is hoped, will be a non-lethal alternative to the current shark safety gear.
The Division disseminates its knowledge and expertise through scientific publications and presentations at conferences, workshops, and talks to service clubs, user groups and the media. It also provides expert assistance with shark attack prevention on request from other areas (e.g. Cape Town, Port St Johns, Seychelles and Reunion).
The KZNSB has been an active member of the South African National Tagging Program since 1984. The Tagging Program is administered by the Oceanographic Research Institute (ORI) and since its inception in 1984, 5200 registered members have tagged over 285 000 fish of about 350 species. Most of the participants are volunteer anglers, but several research institutes and universities also participate.
The overall recapture rate of sharks released from the nets and drumlines is about 4%. It is interesting to note that the recapture rate of free-swimming ragged-tooth sharks tagged by divers, where there is no capture stress, is higher (10.2%) than that of raggies tagged from the nets and drumlines (4.7%). Recapture rates for other net-tagged species vary, e.g. 4.8% for the blacktip and 4.6% for the tiger shark.The overall recapture rate for injected sharks is 4.6% and 6.5% for the giant guitarfish. To date none of the other tagged rays has been recaptured. Here are some recapture highlights.
Growth and Ageing of sharks
The conservation, management and rational utilisation of shark stocks are receiving increasing global attention. In a local context it is essential to have accurate information on the biology and life history of the various species being exploited in the shark nets to understand the impact of the netting program on these shark populations. Knowledge of shark age and growth is fundamental to these processes.
The KZNSB conducts regular aerial surveys of the northern KZN coast to determine the number and distribution of whale sharks. The project was initiated in 2001 when the KZNSB was requested by the Branch: Marine and Coastal Management of the Department of Environmental Affairs and Tourism (now referred to as Oceans and Coast) to assess the potential for dedicated whale shark diving on the South African coast. During the surveys, researchers also count the number of whales, dolphins, turtles and manta rays sighted.
Port St Johns
In 2011, the KZNSB was requested by Oceans and Coast to investigate the reasons behind the spate of tragic shark attacks at Port St. Johns, on the east coast of South Africa. Since 2007 there have been 9 shark attacks, 7 of which have been fatal at Second beach, which is PSJs most popular bathing beach.
To better understand the movement patterns of potentially dangerous sharks an array of “listening stations” have been deployed close inshore at Second beach, as well as at other popular beaches in the vicinity of Port St. Johns. These stations are able to detect “listen” for the presence of any shark (within a radius of up to 800m), which has been fitted with an acoustic tag. To date, a total of 3 bull (Zambezi) sharks and a white shark have been caught and tagged off Port St.Johns. Tag detections from these sharks are already yielding some very interesting results. Two of the tagged bull sharks have been detected (by other collaborative studies) as far away as Ponta do’Ouro in Mozambique, the Breede River in the Southern Cape and Port Elizabeth in Algoa Bay. The results suggest that these bull sharks may not be resident at Port St. Johns, but rather transient visitors. We hope that the results from the study can provide an insight into the seasonal occurrence of sharks at Port St. Johns, which in turn can be used to reduce the probability of a person encountering a shark and lessen the risk of shark attack
The KZNSB has been monitoring sea surface temperatures, as well as other environmental parameters for the past 20 years. Recently, we have deployed 9 digital “Star-Oddi” temperature loggers at netted beaches between Richards Bay and Port Edward and one at Protea banks. The loggers have been supplied by the Oceanography Division of the Department of Environmental Affairs. The loggers are extremely sensitive to within 0.025°C. They will collect data as part of a collaborative long-term monitoring program investigating global climate change along the South African coastline. Other partners include the South African Environmental Observation Network and the South African Institute for Aquatic Biodiversity. In the short-term, data from the loggers will be used to better understand the movement patterns of sharks in response to water temperature profiles. An example of the type of data these loggers collect is presented below.