Theses and Dissertations


Title: Vertical distribution, size structure, and habitat association of four Blennidae species on gas platforms in the northcentral Gulf of Mexico

Name: Topolski, Marek F.

Degree: MS

Chair: Stephen T. Szedlmayer

Resides:

University: Auburn University

Location: Auburn, Alabama

Date: 2001

Pages: 86

Keywords: Blenny,Gulf of Mexico,gas platforms,population structure,fish distribution

Abstract:

Gas and petroleum provide structure at all depths of the water column, which is atypical for the continental shelf ecosystem of the northern Gulf of Mexico. However, few studies have examined the demersal reef fish community on platforms, which is dominated by Blenniidae species. In this study, the abundances of four blenny species (Hypsoblennius invemar, Hypleurochilus multifilis, Parablennius marmoreus, and Scartella cristata) were surveyed in July and August 1999 on two gas platorms 14 and 24 km southeast of Dauphin Island, Alabama. Blennis were surveyed on the platform legs at depths of 3, 10.5, and 18 m and separated into three size classes: small (15-51 mm TL), intermediate (52-102 mm TL), and large (103-153 mm TL). For each species, abundance decreased as depth increased. Abundance of H. invemar averaged 10 fish m-2 at 3 m and 1 fish m-2 at 18 m, H. multifilis averaged 23 fish m-2 at 3 m and 6 fish m-2 at 18 m, P. marmoreus averaged 6 fish m-2 at 3 m and 2 fish m-2 at 18 m, and S. cristata averaged 89 fish m-2 at 3 m and 0 fish m-2 at 18 m. Most individuals observed were in the small size class. The smallest size class contributed 61% of blennies at 3 m (79 fish m-2), and 89% at 18 m (11 fish m-2). The most abundant blennies observed were small and intermediate S. cristata at 3 m. Large blennies at 3 m also were mostly S. cristata while all other species had few large individuals. Small H. invemar were 2-5 times more abundant compared to intermediate sized individuals and most (85%) H. multifilis were small. Small and intermediate P. marmoreus were equally abundant at 3 and 10.5 m. Blennies were extremely abundant in this study, with abundance ranging from 3-16 times greater than previously reported on platforms in the nothern Gulf of Mexico. Because blennies are closely associated to the substrate, four 20x20 cm substrate samples were taken at each survey depth from one leg of each platform, and found to differ among depths based on principal components analysis. Balanus and Megabalanus antillensis barnacles dominated the substrate communities. Balanus accounted for 59% of the variability in intermediate blenny abundance, while M. antillensis accounted for 15% of the variablility in large blenny abundance. Small blenny abundance was correlated with barnacle abundance, although Balanus and M. antillensis partial correlations were not significant. The positive relationship between blenny and barnacle abundance indicates that blennies without adequate refuge are removed by the larger piscivores also associated with platforms in the northern Gulf of Mexico.

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