Missing limbs in species that do not reproduce asexually may indicate sub-lethal predation. Recruitment, migration and mortality ultimately determine the spatial and temporal distributions of the starfish populations in the Heron Reef assemblage. There is a distinction to be drawn between reproduction and recruitment as well as between predation and mortality. Recruitment is a process that is complete only when an offspring reaches maturity and reproduces itself. Similarly, predation may only be sub-lethal and autotomised limbs may be regenerated or may become asexual recruits.
Starfish mortality occurs only when all fragments of a starfish have died.
For logistical reasons, it was decided not to examine potential predators in this study. Likewise, a detailed examination of larval settlement processes was not undertaken. Migration of starfish is poorly understood as there is considerable difficulty in relocating tagged specimens particularly in autotomous species. However, the interaction between the major determinants of population size mentioned above will influence the size-frequency distributions of each species. These distributions will be compared over time at Heron Reef and with size-frequency data from other localities.