STRUCTURAL INFLUENCES OF ARTIFICIAL AND NATURAL HABITATS ON FISH AGGREGATIONS IN ONSLOW BAY, NORTH-CAROLINA

Structural complexity of artificial and natural habitats may be respon sible for aggregating and maintaining fish populations. Visual assessm ents of fish assemblages were conducted in 1989 and 1990 in Onslow Bay , North Carolina, to quantify pelagic and demersal fishes associated w ith a natural rock outcrop and two experimental treatments of artifici al habitats. The vertical relief component of both experimental habita ts was held constant, resulting in an experimental design which allowe d for a test of the effects of structural volume and complexity on fis h abundance and pelagic prey/predator interactions. Experimental habit ats were deployed 60 m perpendicular to a natural rock ledge in 25.5 m of seawater and floated 3 m off the bottom. Data supported the hypoth esis that fish abundance is directly proportional to structural volume and complexity. Species richness and assemblage similarity indices in dicated that experimental habitats deployed 3 m off the substrate and in close proximity to one another aggregated similar fish species rega rdless of structural volume and complexity. Analyses of pelagic fish a bundance data suggested inverse relationships between predator and pre y abundance. As shelter availability decreased, pelagic baitfish abund ances decreased and predator abundances increased.