Catching and tracking the world's largest Zambezi (bull) shark Carcharhinus leucas in the Breede Estuary, South Africa: the first 43 hours

Abstract

The Zambezi or bull shark Carcharhinus leucas is a large, predatory shark that occurs in warm-temperate, tropical and subtropical coastal and estuarine systems worldwide. To confirm reports of Zambezi sharks in the Breede Estuary on the south-west coast of South Africa, a survey was undertaken during 20–26 January 2009. On 24 January, a large female Zambezi shark was caught on rod and reel. Measuring 400 cm total length and 320 cm precaudal length, it is the largest recorded Zambezi shark. Furthermore, its occurrence in the Breede Estuary is the southernmost record of the species, extending its previously documented range by 366 km. The shark was tagged with a continuous acoustic tag and tracked for 43 consecutive hours. During that period, it swam as far as 20 km upstream, but it also briefly exited the estuary and travelled 2 km out to sea. Most of the time (24%) was spent 11–13 km upstream, where it actively inspected boats and shore-anglers, a behaviour considered to be an opportunistic foraging strategy. Estuaries appear to represent critical habitats in the life history of Zambezi sharks.