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Alternate Title

Spatial Variation in Fish Density at Three Petroleum Platforms as Measured with Dual-Beam Hydroacoustics

Abstract

Despite the number and ubiquitous placement of petroleum platforms in the northern Gulf of Mexico, little information exists on associated fisheries resources due to the difficulties of sampling these sites with traditional fish census methods. From 1994 to 1996 dual-beam hydroacoustics were employed on quarterly research trips to measure the density and in situ target strengths of fishes associated with petroleum platforms in 20, 60, and 219 m of water. Density varied significantly with platform, distance from the platform, depth, and platform side. Platforms on the continental shelf had a near-field area of influence of approximately 18 m, whereas the near-field are of influence for the site on the continental slope was 10 m, although the relationship was not as well defined as the other sites. Average estimated abundance over the study period was 26,347 at the 60-m site, 13,444 at the 20-m site and 11,224 at the 219-m site. Fishes were distributed throughout the water column at the sites on the continental shelf, whereas on the continental slope (water depth 219m), over 88% of the fishes were found in the upper 60 m of the site.

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