Date of Award

11-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Abstract

High fishing pressure and limited natural habitat characterize the otherwise barren northwestern Gulf of Mexico. South Texas lacks extensive research of local natural and artificial reefs, and few studies report fish community and sportfish analysis of different reef densities. To alleviate this lack of data, fish abundances were monitored at different reef configurations in the PS-1047 Reef, 13 km off Port Mansfield, Texas, where 4000 concrete culverts were placed in 2011. Four culvert categories (CC1: 1-30 culverts, CC2: 31-70 culverts, CC3: 71-120 culverts, and CC4: 121-190 culverts in a 30-m radius), natural reefs and bare areas were sampled. Species abundances were assessed with 15- min SCUBA surveys, and total lengths of commercially valuable Lutjanus campechanus were measured. In summer 2013, water temperatures were warmer (25.1 ± 0.4°C), and surveys had significantly more adults and more even juvenile populations than in the summer of 2014 (22.8 ± 0.2°C). No fishes were observed at bare areas, whereas sites with structure had 186 ± 28 individuals from 13 ± 1 species. Fish communities did not significantly differ between reefs, yet significantly more adult individuals were seen on natural reefs than CC1, CC2, and CC4. CC3 resembled natural reefs with similarly high species richness and total abundance values. Lutjanus campechanus were found at all sites with structure, with an average 41 ± 6 individuals per site, and abundances did not significantly differ among reef categories. CC1 exhibited the largest Lutjanus campechanus, 362.9 ± 8.7 mm, whereas all other reef categories exhibited average lengths ranging from 296.5 to 322.8 mm. Longer individuals at CC1 may result from aggressive behaviors exhibited at sites with less suitable habitat. Using a previous study that assessed total length to age ratios in South Texas, the predicted age of Lutjanus campechanus was two years old. Findings suggest that culvert reefs are substantial improvements to otherwise bare areas, and reefs with about 100 culverts closely mimic species diversity of nearby natural reefs. Thus, it is recommended that future culvert reefs be deployed with 100 culverts in 100 m increments to cover four times more area than at PS-1047.

Granting Institution

University of Texas Brownsville

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