Population characteristics of Indo-Pacific humpback dolphins at Richards Bay, South Africa : implications for incidental capture in shark nets

The population characteristics of Indo-Pacific humpback dolphins ( Sousa chinensis ) were investigated at Richards Bay, South Africa, from April to October 1998. This area has the highest incidental catches of humpback dolphins in shark nets on the KwaZulu- Natal coast. A minimum of 181 individuals were individually identified in a boat-based photo-identification study and this sampled population appeared to be open in nature. Long-term photo-identification suggested that some humpback dolphins display longdistance movement patterns (up to 150 km), while other individuals display long-term residency within the KwaZulu-Natal area. Investigation into the associations between individual humpback dolphins yielded low and varying levels of affiliations. Unfamiliarity and naivete of individual dolphins to netted areas seemed to be the main factors affecting captures in shark nets.