Spatial variation in concurrent settlement of three damselfishes: relationships with near-field current flow.

Abstract

Replenishment of local populations of reef fishes typically occurs via settlement of planktonic larvae, a process that is variable in space and time. We examined spatial variation in settlement of three species of damselfishes (genus Dascyllus) in relation to variation in average near-field current speed. Although the larvae of these species colonized at the same times, they repeatedly exhibited qualitatively different spatial patterns of settlement in the lagoons of Moorea, French Polynesia. Each damselfish had a unique, temporally consistent pattern of variation in settlement relative to among-site variation in near-field flow speed. At the speeds encountered, settlement was related linearly to increasing average current flow for yellow-tail dascyllus (D. flavicaudus), was a positive but decelerating function for humbug dascyllus (D. aruanus) and was a hump-shaped function for three-spot dascyllus (D. trimaculatus). Such qualitatively different relationships could arise if variation in current speed affected an individual's probability of settling differently among the species. The generalized relationships between flow speed and settlement of these species predicted well the pattern of covariation in settlement of these species among new sites where the availability of suitable habitat was standardized. These findings imply that differences in larval abilities in the near-field can result in distinctly different patterns of larval colonization among species, even in the absence of any other source of variation.