| Abstract: | Abstract 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 assemblages. However, body size has substantial effects on processes that affect competitive relationships between species: (i) small, recently recruited fish, which usually(?) suffer high mortality, can dominate total abundance and strongly influence the dynamics of the relative total abundances of different species, while having little effect on interspecific biomass relations; (ii) numeric abundance and biomass of a species can vary independently, due to habitat variation in population size-structure resulting from variation in mortality and growth, as well as habitat selection; and (iii) population size-structure affects the potential for and outcome of interspecific competition due to (a) ontogenetic change in types of resources used, (b) levels of resource needs being dependent on individual and species biomass rather than numbers, (c) advantages due to large size in behavioural contests, (d) variation in population size-structure being linked to habitat preference, which affects expression of competitive dominance, and (e) size dependency in the development of interspecific resource-sharing relationships. Assemblage-level analyses that ignore such size effects may fail to detect important effects of interspecific interactions. |
