IMPLICATIONS OF BODY-SIZE FOR INTERSPECIFIC INTERACTIONS AND ASSEMBLAGE ORGANIZATION AMONG CORAL-REEF FISHES

Population size-structure is often ignored in assemblage-level studies of reef fishes, which usually rely on static and dynamic patterns of relative total abundance to infer what mechanisms organize those assem blages. However, body size has substantial effects on processes that a ffect competitive relationships between species: (i) small, recently r ecruited fish, which usually(?) suffer high mortality, can dominate to tal abundance and strongly influence the dynamics of the relative tota l abundances of different species, while having little effect on inter specific biomass relations; (ii) numeric abundance and biomass of a sp ecies can vary independently, due to habitat variation in population s ize-structure resulting from variation in mortality and growth, as wel l as habitat selection; and (iii) population size-structure affects th e potential for and outcome of interspecific competition due to (a) on togenetic change in types of resources used, (b) levels of resource ne eds being dependent on individual and species biomass rather than numb ers, (c) advantages due to large size in behavioural contests, (d) var iation in population size-structure being linked to habitat preference , which affects expression of competitive dominance, and (e) size depe ndency in the development of interspecific resource-sharing relationsh ips. Assemblage-level analyses that ignore such size effects may fail to detect important effects of interspecific interactions.