EFFECTS OF GAS PRODUCING PLATFORMS ON CONTINENTAL-SHELF MACROEPIFAUNAIN THE NORTHWESTERN GULF-OF-MEXICO - ABUNDANCE AND SIZE STRUCTURE

Macroepifaunal populations near three active gas-producing platforms w ere studied as part of the Gulf of Mexico Offshore Operations Monitori ng Experiment (GOOMEX) using a near-field (50-100 m), far-field (3 km) collection strategy. When differences in catch per unit effort (CPUE) existed, they were species and site specific. Size effects were not s olely due to sexual dimorphism. Differences in size and abundance did not covary. General responses to the presence of platform structure or other characteristics common to gas-producing platforms were not obse rved. CPUE was site (platform) specific, indicating that epifauna resp onded to the unique physical and chemical characteristics of each plat form. The frequency of significant near-field/far-field differences de clined with increasing depth as did the frequency of significant seaso nal and time-of-collection differences in size and CPUE, suggesting th at platforms affect adjacent community structure more strongly in shal low water and that seasonality and behavior patterns may be important promoters of this effect. Significant differences occurred no less fre quently in the most mobile species (penaeid shrimp) than in the much l ess mobile starfish and scallops. Accordingly, discrete populations of mobile epifauna maintain their coherence for significant periods, whi ch permits differential effects produced by nearness to platforms to b e expressed in some of the most mobile invertebrates on the shelf.