Artificial reefs facilitate tropical fish at their range edge

Spatial planning increasingly incorporates theoretical predictions that artificial habitats assist species movement at or beyond range edges, yet evidence for this is uncommon. We conducted surveys of highly mobile fauna (fishes) on artificial habitats (reefs) on the southeastern USA continental shelf to test whether, in comparison to natural reefs, artificial reefs enhance local abundance and biomass of fishes at their poleward range margins. Here, we show that while temperate fishes were more abundant on natural reefs, tropical, and subtropical fishes exhibited higher abundances and biomasses on deep (25-35 m) artificial reefs. Further analyses reveal that this effect depended on feeding guilds because planktivorous and piscivorous but not herbivorous fishes were more abundant on artificial reefs. This is potentially due to heightened prey availability on and structural complexity of artificial reefs. Our findings demonstrate that artificial habitats can facilitate highly mobile species at range edges and suggest these habitats assist poleward species movement.