Experimental Analysis of Structural Versus Trophic Importance of Seagrass Beds. II. Effects on fishes, decapods and cephalopods

The relative influences that seagrass structure and trophic resources exert on the species richness, abundance, biomass and productivity of epibenthic fishes and invertebrates were assessed using manipulative field experiments. All community variable increased significantly when seagrass structure was added to experimental plots but were little affected by enhanced food resources in the form of debris-associated prey. Epibenthic productivity therefore appears much less strongly coupled with food availability than was macrofaunal and meiofaunal productivity, possibly because of a lag between epifaunal food accumulation and fish recruitment. Gut content studies nevertheless indicated that sand-dwelling as well as seagrass-dwelling fishes in the vicinity of seagrass patches were primarily foraging on large amphipods and other invertebrates associated with the seagrass patches, and that the mean size of sand-dwelling species was elevated near Artificial Seagrass Units. Results of this study suggest that fishes and epibenthic invertebrates preferentially select seagrass beds over bare areas for settlement but do not initially discriminate between beds with different levels of food resources.