Date of Award

2001

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

First Advisor

Charles A. Wilson

Abstract

Surveys of ichthyoplankton assemblages were conducted from four oil and gas platforms located in the northern Gulf of Mexico from November 1994 through July 1997. Diurnal collections, supplemented with light trap collections from the surface and -20 m depth, were taken quarterly during 1994 and 1995. Quarterly ichthyoplankton sampling at dawn and dusk only during 1996 and 1997 were supplemented with surface "lighted plankton net" collections. Of the 36,676 individuals collected, epipelagic (neretic and oceanic Clupeiformes, neretic Carangidae and Lutjanidae, as well as oceanic Scombridae) and mesopelagic (Myctophidae and Gonostomatidae) families comprised the majority of the ichthyoplankton. Reef-dependent (e.g., Pomacentridae, Labridae, and Acanthuridae) families that dominated the adult fish communities at the platforms were either absent or very rare from both ichthyoplankton and light trap collections. Large-scale water mass movements, which primarily determine the transport of planktonic organisms as well as the linkage between potential source (natural reefs, hard bottom banks, and other platform structures) and sinks (platform artificial reef sites) were investigated with blended TOPEX/POSEIDON and ERS-2 radar altimetry. Serranid larvae collected from the plankton were aged by use of sagittal otoliths in order to estimate their transit time from natal source areas. Transit time in the plankton averaged 14.5 days. Seasonal transport envelopes showed that recruitment to mid-shelf and shelf-break platforms were influenced primarily by mesoscale warm-core and cold-core eddies. Within these seasonal envelopes, the numbers of artificial reef platforms potentially serving as source locations for recruitment greatly outnumbered the natural reef sites. Scuba diver and remotely operated vehicle surveys of juvenile and adult stage reef-dependent species were also conducted on the mid-shelf and shelf-break platforms. These were compared to underwater video footage of natural reef sites (National Marine Fisheries Service, SEAMAP fish trap/video gear) in order to establish correspondence between the taxa supplied to the platforms and the surrounding hard-bottom communities. Bray-Curtis similarity cluster analysis and multidimensional scaling of adult and juvenile reef-dependent fish communities showed that platform habitats had a biological character more like natural reef sites found in the eastern Gulf of Mexico, where little recruitment was shown to originate.

ISBN

9780493563350

Pages

195

Share

COinS