Identifier

etd-0407103-164922

Degree

Master of Science (MS)

Department

Forestry, Wildlife, and Fisheries

Document Type

Thesis

Abstract

Marsh terracing and coconut fiber mats are two restoration techniques currently being implemented at Sabine National Wildlife Refuge. We tested two hypotheses related to these restoration techniques: (1) marsh terracing enhances nekton assemblages, so that nekton use is similar to those at natural marsh edges, and (2) coconut matted marsh edges enhance SAV recruitment, so that nekton use is similar to those found at natural marsh edges. Samples from terraces and coconut matted marsh were compared to samples from the natural marsh and open water habitats. We measured the following variables at each habitat: (1) nekton density and abundance, (2) nekton biomass, (3) nekton size, (4) nekton diversity, and (5) nekton species composition. Using a collapsible throw trap with 3 mm mesh and a 3 x 2 m straight seine, 180 nekton samples were collected at four sampling dates from winter 2001 to fall 2002. Six habitat types were sampled: (1) natural marsh edge (< 1 m from marsh - water interface), (2) coconut matted marsh edge, (3) terrace edge, and (4), (5), (6) open water (50 m from marsh - water interface for all 3 edge types). Environmental variables that may be influenced by restoration status were also monitored at each habitat. Samples from terraces and coconut matted marsh were compared to samples from the natural marsh edge and open water habitat. Results indicated that nekton variables at coconut matted edge and open water, natural edge, and terrace edge were not significantly different (p > 0.332). Nekton density, biomass, and diversity were lower in open water habitats associated with natural marsh and terraces than in the other four habitats (p < 0.0001). Coconut matted and natural marsh edges had significantly higher numbers of some benthic dwelling species (e.g. blue crab Callinectes sapidus, white shrimp Litopaenaus setiferous, naked goby Gobiosoma bosc, clown goby Microgobius gulosus, Gulf pipefish Syngnathus scovelli) than terrace marsh edges (p < 0.0004), potentially due to differences in substrate caused by construction of the terraces. Researchers have suggested that decreased benthic habitat quality at dredged material marshes is related to an impaired infaunal community and differences in sediment texture. At Sabine NWR, terracing and coconut matting increased nekton utilization 4.5 times above that in open water habitat by enhancing and increasing marsh edge relative to open water. The value of terrace and coconut matted marsh habitat for individual species may vary depending on their niche requirements. Future research on terrace success at providing nekton habitat should address nekton growth rates and correlate nekton composition to the infaunal community.

Date

2003

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Megan K. G. La Peyre

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