Port St Johns shark study

November 23, 2011. The KwaZulu-Natal Sharks Board (based in Umhlanga) is to embark on a study of the sharks of the Port St Johns area in the Eastern Cape. This research was commissioned and funded by Branch: Oceans and Coasts of the national Department of Environmental Affairs, following four fatal shark attacks – three in 2009 and one in 2011 – at Second Beach, the most popular swimming beach in the town.

The aim of the research is to obtain a better understanding of the community of large species of sharks in the area and to investigate factors which may have contributed to the recent shark attacks. The study will involve several sampling trips over the next 13 months, covering each of the four seasons.

Sharks will be caught using baited hooks; each individual will be identified, sexed and measured and then tagged and released. Of particular interest are Zambezi and tiger sharks, two species which have been implicated in attacks at Port St Johns. Each captured individual of these two species will be fitted with an acoustic tag which emits a unique signal every few minutes. Underwater receivers placed at several locations on the seabed in the Port St Johns area will detect the presence of the tagged sharks as they move around.

This is the first time that a dedicated study of the sharks of Port St Johns has been undertaken. Reports from anglers and divers indicate that the area has a healthy community of sharks, particularly during the winter when the annual sardine run attracts large numbers of predators, such as copper, dusky, blacktip and spinner sharks, to the Wild Coast. These species pose little threat to beach users at Second Beach.

The researchers are most interested in the sharks that are present during the summer months, when the all the attacks occurred, and when tiger and Zambezi sharks are most likely to frequent the area.

The sardine run attracts large numbers of predators, such as copper, dusky, blacktip and spinner sharks, to the Wild Coast

The Umzimvubu River, one of the largest rivers on the South African east coast, enters the sea at Port St Johns. It is one of several river systems used by Zambezi sharks as nursery grounds for their newborn. These young sharks feed on the rich fish stocks within the estuarine system and use the murky water to reduce their chances of being eaten by other large marine predators. Although the young sharks are too small to pose a threat to the surfers and swimmers at Second Beach, one of the aspects of the research will be to learn more about their use of the estuary.

The research also aims to identify activities which may attract potentially dangerous sharks inshore at Port St Johns. There have been several suggestions put forward by the locals but to date nothing has been confirmed and it is conceivable that no human activities are responsible.

Finally, it is anticipated that the research will allow the formulation of recommendations that would reduce the risk of shark attacks in the future.

Issued by the KZN Sharks Board