Artificial Reefs: The Importance of Comparisons with Natural Reefs

Abstract

Methods used to evaluate the performance of an artificial reef will vary according to the purpose for which the reef was built. To determine how well artificial reefs mitigate losses due to human activities on natural reefs, the performance of artificial reefs should be evaluated using contemporaneous comparisons with relatively undisturbed natural reefs. Unfortunately, comparisons between artificial and natural reefs are typically confounded by differences in reef size, age, and isolation. We compared colonization and subsequent assemblage structure of reef fishes on coral and artificial (concrete block) reefs in which reef size, age, and isolation were standardized. Species richness and fish abundance (all species combined) were greater on reefs of natural rather than artificial structure, but substantial differences in species composition were not detected. Our results suggest that artificial reefs with structural complexity and other abiotic and biotic features similar to those of natural reefs will best mitigate in-kind losses of reef fish populations and assemblages from natural reefs. Because of the open nature of most reef fish populations, estimating the contribution of artificial reefs in attracting v producing reef fishes will require a regional assessment of rates of demographic processes on both artificial and nearby natural reefs.