Studies on southern Australian abalone (Genus Haliotis). III. Mortality of two exploited species

Abstract

The natural mortality of populations of H. laevigata and H. ruber was measured at two sites off the South Australian coast, West Island and Tipara Reef, which were closed to commercial fishing for the duration of the experiment. Abalone were individually marked with numbered tags and censuses taken of the marked populations periodically over several years. Examination of the data for H. laevigata at West Island showed that there was no significant age dependence in mortality, and that the probability of sighting an animal was independent between successive visits. The average annual natural mortality rate for H. laevigata at West Island was estimated to be 0.26 (s.e. 0.06) and at Tipara Reef to be 0.22 (s.e. 0.10). The mortality rate estimates for H. ruber were 0.36 (s.e. 0.28) at West Island and 0.21 (s.e. 0.10) at Tipara Reef.