Mortality of post‐settlement abalone Haliotis iris caused by conspecific adults and wave exposure

Abstract

Experimental studies of post‐settlement abalone (Haliotis iris Martyn) indicate that wave exposure and conspecific adults may be important sources of mortality. In aquarium studies, exposure of post‐settlement abalone to grazing by sea urchins (Evechinus chloroticus) and starfish (Patiriella regularis), animals common in the subtidal habitat of H. iris, resulted in similar survival to control treatments (no grazers). However, in the presence of conspecific adults, the survival of post‐settlement juveniles was approximately half that of control treatments. The major cause of mortality was evidently pedal smothering by adults. Similar results were obtained in field studies in which survival of recently settled abalone was greater in the absence of conspecific adults. Field studies also revealed that the differences between two bays exposed to contrasting wave action were a significant source of variation in post‐settlement mortality. Survival of recruits was greater in the sheltered bay compared with the bay exposed to ocean swells.