Abstract
Twenty six species of coral reef fishes in 11 families producing pelagic eggs were observed to spawn at a shelf edge coral reef off southwestern Puerto Rico. Data are included on the time, location, seasonality and behavior of all species. Most species had lengthy spawning seasons with an overall winter peak of activity. Only Acanthurus coeruleus demonstrated a clear lunar periodicity to its group spawning. Spawning on all phases of the moon was found for many species. Pair spawning only was seen in 23 fishes while 3 species both pair and group spawned. None group spawned without also pair spawning.Most fishes spawned in the late afternoon from the hour before up until sunset. The closer to sunset a species spawned, the narrower was the time range when spawning was observed. Two scarids, Scarus taeniopterus and S. vetula, were found to spawn only in the morning and a third parrotfish, Sparisoma viride, spawned both morning and afternoon.Predation by piscivores on spawning adults was rare while predation by zooplanktivores on newly released eggs was only occasional. Tidal currents were not significant at the study site, due to low tidal amplitude, and spawning occurrence was not correlated with tidal phase. It is believed late afternoon spawning serves to synchronize spawning in areas where distinct tidal currents do not occur.Winter spawning and migration to shelf edge areas for spawning may be adaptations to glacial period reef conditions rather than mechanisms for increasing chances of survival of the larvae. It is unlikely the spawning populations studied are self-recruiting, but this may occur elsewhere.Timing of spawning is believed to be determined by the need to coordinate activity of adults and is not related to oceanographic conditions that might increase chances of survival of the larvae. Fishes which probably have quite different requirements for larval development (“inshore” and “offshore” development), based on knowledge of larval morphology and early life history, spawn at the same time. If the entrainment of eggs and larvae into particular oceanographic conditions was important, a disparity in spawning times would be expected to exist between species with different larval requirements. It is believed the timing of spawning is not random, but the outlook for survival of any given clutch of eggs is uncertain.