Reef fish associations with sea urchins in an Atlantic oceanic island

Abstract

Many reef fish are known to be associated with particular microhabitats that provide food and refuge, such as branching corals, gorgonians, macroalgal beds and sea urchins. We investigate the association of reef fishes with the long-spined sea urchin Diadema antillarum in shallow reefs of Trindade Island, southeastern Brazil. A total of 1283 fish individuals from seven families and nine species were associated with 495 sea urchins. Sea urchins provide important shelter especially for juveniles of the Noronha wrasse, Thalassoma noronhanum. Larger fishes were found at higher densities associated to sea urchins with larger spines. At reefs lacking structurally complex organisms, such as branching corals, sea urchins can be an important refuge for juveniles or small-bodied reef fish species, influencing their distribution and acting as ecosystem engineers.