Title page for ETD etd-11112004-171053


Type of Document Master's Thesis
Author Birdsong, Timothy W.
Author's Email Address tbirds1@lsu.edu
URN etd-11112004-171053
Title Complexity and Nekton Use of Marsh Edge Habitats in Barataria Bay, Louisiana
Degree Master of Science (M.S.)
Department Renewable Natural Resources
Advisory Committee
Advisor Name Title
Megan K. La Peyre Committee Chair
Charles A. Wilson Committee Member
D. Allen Rutherford Committee Member
William E. Kelso Committee Member
Keywords
  • marsh edge
  • essential fish habitat
  • complexity
Date of Defense 2004-11-09
Availability unrestricted
Abstract
This study examined the effects of intrahabitat variability on marsh edge use by fishes and decapod crustaceans. The objectives were to (1) identify quantitative measures of habitat complexity that describe the structural design of marsh edge habitats, and (2) examine differences in nekton use between cut-bank and gently sloping marsh edge habitats. The study was conducted in Barataria Bay, Louisiana at 75, 10-m marsh edge study sites. Monthly seining was conducted in fall 2003 and spring 2004 and measures of habitat complexity were recorded at each sample location. Indices of tidal inundation and site exposure to wind and wave action were calculated. Results showed significantly greater complexity (i.e., irregularity, elevation, bank height, bank undercut, vegetation densities and percent vegetated cover) at cut-bank edges over gently sloping edges (P < 0.0001). Nekton diversity (fall: P = 0.0236, spring: P = 0.0297) and mean abundance of bay anchovy Anchoa mitchilli (fall: P = 0.0010) were also significantly greater at cut-bank edges over gently sloping edges. Lower mean elevation at gently sloping edges resulted in significantly greater levels of inundation over cut-bank edges (P < 0.0001), providing earlier and prolonged use of inner marsh habitats. Mean abundances of marsh residents that frequent the vegetated marsh surface (naked goby Gobiosoma bosc (fall: P = 0.0055), gulf killifish Fundulus grandis (fall: P = 0.0280), and grass shrimp Palaemonetes pugio (fall: P = 0.0017) were significantly greater at gently sloping edges over cut-bank edges. Several associations were observed between nekton community parameters and measures of habitat complexity, including strong positive correlations between species diversity (fall: P < 0.0001, spring: P < 0.0001), species richness (fall P = 0.0001, spring P = 0.0029), and exposure to wind and wave action. Differences in use between cut-bank and gently sloping edges and associations between nekton variables and measures of habitat complexity suggest that differences in habitat structure exist among marsh edge habitats and that these differences do influence habitat selection by nekton. This study highlights the need for methods that provide more explicit identification of EFH by determining relationships between productivity and the different habitats used by aquatic organisms.
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