Environmental Stochasticity of Spatiotemporal Recruitment Patterns in Coral Reef Fish (Tahiti, French Polynesia)

Abstract

The densities of coral reef fish juveniles often vary temporally due to different spawning and recruitment periods throughout the year and spatially due to the quality of nursery habitats. Juveniles carefully select their nursery habitat based on numerous factors, notably environmental parameters and the presence or absence of predators or conspecifics. To identify environmental and ecological factors that controls the juvenile fish distributions, fish populations and physicochemical water parameters were characterised from May to December 2020 on five contrasting habitats along the coastline of Tahiti (French Polynesia). Although juvenile fish diversity varied between the five habitats, density did not significantly differ from site to site. It emerged that density was strongly linked to temporal recruitment periods but was also positively correlated to the presence of adult conspecifics; thus differing from the common preference for zones with fewer adults. Water parameters were also linked to juvenile distributions, with more juveniles of all species in warmer water, and more herbivore juveniles in lower pH conditions. The nutrient loads did not have significant effects on juvenile densities. Overall, this study highlights that, beyond widely studied factors such as habitat type and adult populations, certain physicochemical parameters can also be indicative of juvenile fish distributions on coastal nursery habitats.