Bottlenose dolphin Tursiops truncatus distribution in Natal's coastal waters

Abstract

The distribution of bottlenose dolphins Tursiops truncatus between the Tugela River mouth, Natal, and the Transkei border was investigated. Comparison of sighting rates between the periods 1974–1978 and 1984–1988, accumulated by personnel servicing shark nets at 42 localities, indicated six areas where dolphins were sighted more frequently. These preferred areas were similar in length (32,7–41,9 km). Behavioural data suggested that the preferred area centred on Margate represents the home range of a local dolphin population. Analysis of dolphin catches in the nets indicated that they are caught at random along the coast, although there was an association between catch and sighting rates. Mean water clarity at each beach was not correlated with either sighting or capture rates at the same beach for the period 1984–1988. Sighting rates of groups of bottlenose dolphins decreased some five- to tenfold in the decade between the periods 1974–1978 and 1984–1988, suggesting a decline in the number of bottlenose dolphins inhabiting the Natal coast.