Environmental influences on the diel timing of spawning in coral reef fishes

Abstract

Multiple hypotheses have been proposed regarding the adaptive nature of different diel reproductive cycles observed in coral reef fishes.This study quantified the spawning patterns of 11 different reef fish species at Johnston Atoll (Central Pacific), while making simultaneous measurements of the environmental factors likely to affect their spawning behaviors.The environmental variables measured (time of day, tides, current velocity, current speed and abundance of piscivores) were correlated with observed spawning outputs through multifactorial analyses.High interspecific variability in spawning patterns was found among the 11 monitored species.The majority of species spawned at a specific time of the day, in agreement with the timing of spawning described at other locations, indicative of a fixed general response by fishes across distribution areas.Spawning of most fishes with daytime spawning peaks was correlated with local changes in current direction and predatory risks, suggesting responses designed to reduce the mortality of propagules and adults.Dusk-spawning species generally did not respond to changes in flow direction and predator abundance, most likely due to their short spawning periods and the reduced predatory pressures that occurred at dusk.Tides did not seem to be used exclusively as synchronizing cues by adult fishes for spawning.The influence of current speed in determining diel timing of spawning varied among species; some avoided spawning during low current speeds while the majority showed no clear response.