A Comparative Analysis of the Fish Assemblages Associated with Old and New Shipwrecks and Fish Aggregating Devices in Onslow Bay, North Carolina

As an aid to determining the best artificial habitat for use by North Carolina's pelagic sport fishermen, we examined the fish assemblages associated with three structurally different artificial reefs: an old dredge wreck (ca 1940s); a new tugboat wreck (placed February 1985); and four arrays of FADS (deployed May, 1985). The fish populations were estimated by use of the stationary diver survey technique. Surveys were performed on 19 days (weather permitting) during the period of June to December 1985. A total of 48 species was recorded in association with the structures during the survey period. Species richness was highest at the dredge (40 species), high on the recently sunken tugboat (37 species), and, low on the FADs (16 species). Species diversity for each site followed the same pattern, and species evenness did not differ significantly between the dredge and tugboat. Dense mixed schools of semipelagic baitfish (Decapterus punctatus and Harengula jaguana) were the most abundant species associated with each structure; however they were more abundant at the FADs than at the tugboat and dredge, and more abundant at the tug than at the dredge. Statistically significant differences occurred in the abundances of eight of the overall ten most abundant species between the tug and FADs, in five of the species between the tug and dredge, and in nine species between the FADs and dredge. The FADs attracted the greatest number of pelagic species, although a number of them were only present as juveniles. Adult Spanish mackerel (Scomberomorus maculatus), little tunny (Euthynnus alletteratus), and cobia (Rachycentron canadum) were present in similar abundances at all sites, while greater amberjack (Seriola dumerili) was more abundant at the dredge and tug than the FADs. Two general temporal abundance curves for structure inhabitants were identified. The first showed a greater abundance of individuals between July and October and exemplified warm water or non-residential species such as Spanish mackerel and blue runner (Caranx crysos). The second type of curve did not show this pattern and was typical of more temperate species such as pigfish (Orthopristis chrysoptera) and spottail pinfish (Diplodus holbrooki).