Fish use of reef structures and adjacent sand flats: implications for selecting minimum buffer zones between new artificial reefs and existing reefs

Artificial reefs are deployed worldwide to enhance fisheries. Placement of artificial reefs relative to nearby existing artificial and natural reefs can influence fish use of these structures, yet no quantitative guidelines exist for selecting optimal distances between new and existing reefs. Here, we documented fish abundance, biomass, species richness, community composition, and key environmental variables on 24 artificial and natural reefs with adjacent sand flats to infer minimum buffer distances around existing reefs where placement of new artificial reefs should be avoided. At each site, we surveyed 4 transects: one 30 m transect across reef structure and 3 consecutive 30 m transects of increasing distance from the reef across sand bottom. Fish abundance, biomass, and species richness were highest on reefs and progressively decreased across adjacent sand flats. Environmental variables influenced these community metrics, but patterns of fish habitat use persisted. Fish community composition shifted gradually from reefs across adjacent sand flats, with fish communities on reefs most dissimilar to communities on sand bottom farthest from the reefs. A minimum buffer of 60 m (30 m around existing reefs plus 30 m around new reefs) or 120 m (60 m plus 60 m) between reefs would encompass 77 and 97%, respectively, of fishes utilizing sand-bottom habitat around each reef. Future artificial reef deployment should maintain these minimum buffer zones between reefs to more effectively enhance fisheries by minimizing attraction of fishes from existing reefs, while also maximizing food resource availability for reef fishes and area for routine reef fish behaviors.