Habitat configuration and availability influences the settlement of temperate reef fishes (Tripterygiidae)

Abstract

To survive, most benthic marine organisms must find suitable settlement habitat. For reef fishes, settlement habitat is often structurally complex, spatially heterogeneous, and dynamic. Consequently, successful settlement is likely to be determined by an interaction between larval delivery and behavior, habitat availability, and structural characteristics (e.g., configuration) of the habitat itself. We examined the effects of habitat configuration and availability on the settlement of New Zealand triplefins (Tripterygiidae), using a field experiment that comprised three habitat treatments and evaluated effects over naturally varying levels of larval supply. Our results suggest that settler density and total settlement are shaped by both the availability and spatial configuration of habitat patches. Highest total settlement occurred in larger, more clumped habitat patches. Lowest total settlement occurred in more dispersed habitat patches of the same size and smaller isolated patches. The densities of recently settled triplefins were lowest in the dispersed patches, and high in both isolated patches and the clumped patches. We speculate that dispersed patches may comprise a lower quality habitat, and/or provide a weaker settlement trigger for both physical and biological reasons. Clumped patches, on the other hand, may provide a stronger settlement cue via baffling of currents, or may represent a higher quality habitat for recently settled triplefins, triggering higher settlement. Our findings indicate that habitat availability can influence abundance of recently settled fish, but the landscape architecture is an equally important determinant of settlement success for triplefins.