Increase in pelagic larval duration and geographical range for reef fish along an oceanic gradient

The structure of reef fish assemblages is known to vary according to numerous environmental factors, in particular reef type and coral cover. However little is known on the potential causes at the origin of species distribution along gradients in reef type and coral cover. The present article analyzed how pelagic larval duration (PLD), geographical range (GRI), habitat and diet specialization may explain the distribution of species and their relative abundance as oceanic influence increases from the coast to outer barrier reefs. This work is based upon 1714 transects representing 837 fish taxa and 1,140,000 individuals. Both mean pelagic larval duration and mean geographical range increased as oceanic influence increased. These two parameters were size dependent, but within a size class these two variables also increased as oceanic influence increased. The probability of occurrence and relative abundance of diet specialists did not vary along this oceanic gradient. On the opposite the relative abundance of coral dwelling species, small species and species with short PLDs or narrow geographical ranges decreased from the coast to the outer barrier reef. Reef fish assemblages would follow a continuum of life history strategies with at one end large, unspecialized species with long PLD, wide GRI and characterized by strong dispersal and colonizing capacities, and at the other end small, sedentary, specialized species with short PLD, narrow GRI and high abundances