Most Australian abalone fisheries are fully exploited and a comparison of the total catch of blacklip abalone, Haliotis ruber, in the three south-eastern states indicates a decline in population size from south to north. The catch distribution from New South Wales parallels that trend. This decline could be due to a decrease in available reef area, lower densities per unit area of reef, or both.

In the absence of fishing there are four determinants of the biomass of a population; recruitment of new individuals, growth and mortality of existing individuals, and area occupied by the stock. Since population sizes differ from south to north, one or more of these factors must be responsible, i.e. lower recruitment, lower growth rates, higher mortality or fewer productive reefs.

In addition to determining the basic population parameters, the basic aim of this research programme was to determine which factor or combination of factors contributed to the apparent declining trend in total population. The same factors would also play some part in New South Wales being the northern limit of the distribution of H. ruber. Another aim was to investigate, at least qualitatively, the association (if any) between sea urchins and abalone.