Importance of postsettlement processes for the population dynamics of Acanthaster planci (L. )

Abstract

It has often been regarded that the greatest influence on population dynamics of invertebrate broadcast spawners will be physical and biological processes acting to control the dispersal and survival of the larval or presettlement phase rather than any process acting after settlement. This has been particularly so with the crown-of-thorns starfish, Acanthaster planci, due to its enormous fecundity and the consequent potential for small changes in rates of larval survival to greatly influence subsequent settlement. However, consideration of the biological, behavioural and habitat characteristics of newly settled and juvenile starfish shows that post settlement processes will be equally, if not more, important in determining population size. We hypothesize that larvae will be influenced to a greater extent by physical than biotic factors, particularly by hydrodynamics that can determine whether competent larvae will encounter reefs. In contrast, we argue that settling larvae and juveniles will be more influenced by predation because of their slow growth and movement, dependence on local food availability, and relatively long juvenile phase. Measurement of mortality rates in the field and isolating settlement from recruitment are identified as having high priorities for future research.