Abstract

Artificial reefs (1.1 x 1.0 x 1.2 m) were built in July 2008 (n = 20) and 2009 (n = 20), 28 km south of Dauphin Island, Alabama, USA, in the northern Gulf of Mexico. Each reef consisted of a polyethylene pallet, with 10 concrete blocks (10 x 20 x 41 cm) and a plastic crate (65 x 35 x 28 cm). We also built 20 larger artificial reefs (8 m3; steel cages 2.5 x 2.6 x 1.2 m). Each year, 10 small reefs were placed at 15 m and 10 were placed at 500 m from the larger cage reefs. Each set of reefs (2 small and 1 large) were placed 1 km apart. All reef fishes were visually counted, videotaped, photographed, and sizes estimated in August 2008, and August and September 2009, by two SCUBA divers. In the lab, all fish in the photographs were identified to species and counted with Image-pro software. There were significantly (p < 0.05) higher abundances of age-0 red snapper, Lutjanus campechanus, on the small reefs placed 500 m (46.1/ m2 ± 8.3) from the larger reefs compared to small reefs placed 15 m away (3.4/ m2 ± 1.8) on all three surveys. We suggest that the typically larger fish (> 300 mm TL) of several species (red snapper, gag Mycteroperca microlepis, gray triggerfish Balistes capriscus, greater amberjack Seriola dumerili) that had colonized the larger reefs resulted in a predator avoidance response by the age-0 red snapper.

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