Large sharks and plastic debris in KwaZulu-Natal, South Africa

Abstract

In total, 28 687 large sharks were caught between 1978 and 2000 in the nets that protect users of the popular swimming beaches of KwaZulu-Natal, South Africa, against shark attack. Over this 23-year period, 53 sharks (0.18% of the catch) were found with polypropylene strapping bands around the body. Less than 1% of the individuals from each of eight species were entangled in this manner. The dusky shark Carcharhinus obscurus was the most frequently entangled species, with 27 individuals (0.47% of the species catch). There was an increase in the incidence of entangled C. obscurus with time. Those examined in the laboratory were significantly underweight. Although entanglement may ultimately result in death, the low incidence recorded in this study is unlikely to affect the populations of sharks concerned. A total of 60 sharks (0.38% of those with recorded stomach contents) had ingested plastic debris. The most common items were packets or sheets. There was no increase in the ingestion of plastics with time. The highest frequency of occurrence was in the tiger shark Galeocerdo cuvier, with 38 individuals (7.5% of tiger sharks examined).