Habitat-limited recruitment of coral reef damselfish

Spatial variation in abundance of reef fishes with dispersing larvae often has been attributed to variation in the supply of new colonists from the pl ankton, which we term "supply determination." We conducted field experiment s with three species of planktivorous damselfishes (Dascyllus flavicaudus, D. trimaculatus, and Amphiprion chrysopterus) to distinguish between the in fluence of supply determination and spatial variation in suitable microhabi tat ("habitat determination") on patterns of abundance, and to evaluate whe ther habitat became limited. In experiments where the abundance of initiall y unoccupied habitat suitable for these fishes was manipulated among a seri es of plots, colonization and population trajectories were followed for up to six years. Additional experiments explored the effect that the densities reached on colonization plots had on settlement. Colonization experiments revealed positive linear relationships between the time-averaged abundance of adults and of new colonists among experimental plots. While consistent with supply determination, the patterns resulted al most exclusively from experimentally imposed variation in the amount of sui table habitat among plots. For both species of Dascyllus, habitat became li mited as densities reached on experimental habitats suppressed settlement b y similar to 80-90%. Spatial variation in the abundance of Amphipiron also mirrored availability of suitable habitat, although for this species we fou nd no compelling evidence that local densities were constrained by anything other than an undersupply of larvae. These results highlight the need to c onsider explicitly patterns of covariation in larval supply and availabilit y of suitable resources, to examine density effects on input as well as los s rates. and to quantify the relative effects of recruitment limitation and resource limitation on local densities.