Factors Affecting Fish Assemblage Development on a Modular Artificial Reef in a Northern Gulf of Mexico Estuary

Twelve plastic (polyolefin), cone-shaped artificial reef modules were deployed in 6.5 m of water in the Choctawhatchee Bay estuary to evaluate their effectiveness as an artificial habitat for fishes. The reef group consisted of four sets, each comprised of three modules or units. Holes (15, 20 and 25 cm diam) were cut into the sides of the modules to evaluate the effect of hole size as well as reef height on the fish assemblage. The point-count, visual census method (5 min, 100 m²) using video/audio was employed to record the dependent variables: number of species, number of individuals, species diversity (H′), and biomass (calculated from total length estimates). During the 13-month survey from October 1987 through October 1988, 31 species were recorded, 20 of which were found during more than 1 month. Most species were apparently derived from the offshore reef fish community. Few estuarine species were associated with the reef. The dependent variables showed both seasonal and colonization features. While the other variables declined with temperature, biomass remained high after the summer influx of species and individuals. Stepwise regression and ANOYA analyses indicated that temperature was the dominant factor associated with variation in the dependent variables. Time of day and tide also had an impact on some variables. Reef specific attributes (i.e., orientation, height, and hole size) had no relationship to the fish assemblage. A DCA analysis exhibited both seasonal and colonization effects and also indicated that the assemblage was dependent on temperature. Four meaningful clusters were formed at level two in a TWINSPAN analysis; the species associations were based on ecological features of the species. The plastic cones were stable throughout the study and attracted a sizable population of the commercially and recreationally important gag, Mycteroperca microlepis. Modular estuarine reefs may prove useful in the management of certain preferred fishery resources.