Identifier

etd-03142016-193545

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

The northern Gulf of Mexico (GOM) contains approximately 2,500 oil and gas platforms, resulting in one of the largest de facto artificial reef systems in the world. As of 2013, 1,227 additional structures had ceased to produce oil and gas and have been decommissioned and removed. While active platforms are lit by high-pressure mercury vapor lights, inactive platforms are only minimally lit for navigation. The positively phototaxic behavior of many fish species causes lit oil platforms to act as fish attraction devices, especially at night. Though a variety of fish species have been reported near these structures, changes in fish abundance, biomass, and species composition in response to artificial light regimes has not been studied thoroughly. Hydroacoustic and video surveys were conducted at two lit and three unlit oil and gas platforms located approximately 130 km off the coast of Louisiana. The goal of this study was to examine the effect of artificial lighting on fish community composition and spatial distribution during the day, night, and during crepuscular periods. Fish abundance changed with depth, season, time of day, and type of platform (lit/unlit), with blue runner (Caranx crysos) as the dominant species at both platform types. Species richness varied with season and time of day, with highest values observed in the summer and during the day. Hydroacoustic surveys were utilized to determine the spatial distribution of fish biomass (MVBS, Sv), which was largely concentrated near the structure and decreased rapidly with distance away from the platform. Platform type did not significantly impact fish biomass. Fish MVBS was highest in depth layer 3 (>60 m) and lowest in depth layer 1 (0-30 m), particularly at night. Regression trees showed a clear area of influence within 45 – 70 m horizontal distance around the structure, as well as fish avoidance behavior of the surface waters (< 9 m). These results suggest that though fishes are attracted to the vertical relief of the structure, they are actively avoiding the artificial light field due to nocturnal predation pressure.

Date

2016

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Cowan, James H., Jr.

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