Abstract

The fisheries aggregation value of oil and gas platforms in the continental shelf waters of the northern Gulf of Mexico is well recognized, but the assessment of early life stages associated with these structures has not been adequately addressed. Ichthyoplankton assemblages were sampled at three offshore platforms: Green Canyon 18 (GC 18; 230 m depth, shelf slope); Grand Isle 94 (GI 94; 60 m depth, mid-shelf); and South Timbalier 54 (ST 54; 20 m depth, inner shelf) with passive plankton nets and light-traps. Family richness was highest at GC 18 (52), followed by GI 94 (43), and ST 54 (42). At the genus level, richness was highest at GI 94 (114), followed by ST 54 (86) and GC 18 (82). Clupeiforms dominated samples at all sites, comprising 59-97% of the total catch. Carangids and scombrids dominated the reef-associated fish assemblages at all sites, with blenniids becoming prominent in inshore collections. Other relatively common reef-associated fish were serranids and lutjanids (GC 18), pomacentrids and opisthognathids (GI 94), and Rhomboplites aurorubens (ST 54). the ichthyoplankton assemblages sampled at each site were relatively dissimilar, based on Schoener's Index of Similarity, with the highest index value for any two sites being 0.45 for GI 94 and ST 54 (0-1 scale). No significant difference was observed between mean Shannon-Weiner diversity indices calculated for plankton net samples at each site. For light-trap samples diversity was lowest at GC 18, significantly higher at GI 94, and then decreased inshore at ST 54. The presence of early preflexion larvae and presettlement postlarvae and juveniles in our collections indicate that both local spawning and settlement/recruitment may be occurring at these platforms

PDF Preview