ASSOCIATIONS AND ABUNDANCE OF SEA-URCHINS AND ABALONE ON SHALLOW SUBTIDAL REEFS IN SOUTHERN NEW-SOUTH-WALES

The densities of the abalone Haliotis rubra and the sea urchin Centros tephanus rodgersii were estimated at five localities on the southern c oast of New South Wales. Abalone were most abundant at localities sout h of Eden but were patchy at all localities and sites. There was no cl ear pattern in the abundance of C. rodgersii among localities but ther e was considerable variation among sites within localities. Densities of abalone and sea urchins were negatively associated within 10-m2 tra nsects at 20% of sites. At the smallest nearest-neighbour scale, the t wo species were segregated. The population structures of abalone diffe red considerably among sites; some populations consisted of single siz e cohorts, whereas others were much more complex. Abalone large enough to be collected legally were rare at all localities and comprised les s than 10% of the total population. Possible reasons for the negative associations between H. rubra and C. rodgersii are discussed.