Master of Science (MS)
Oceanography and Coastal Sciences
I sought to assess the enhancement potential of mimic artificial oyster reefs (MAORs) on trophic dynamics of juvenile estuarine fishes in marsh ponds. Tropic dynamics were investigated by determining the impacts of MAOR addition on meiofauna and macrofauna and then comparing these results to the gut contents and condition of four abundant estuarine fishes: Atlantic croaker (Micropogonias undulatus), bay whiff (Citharichthys spilopterus), sand seatrout (Cynoscion arenarius), and pinfish (Lagodon rhomboides). Samples were collected every other month for two years (March 2009 – 11) employing a Before-After-Control-Impact (BACI) design. Halfway through the experiment (March 2010), two mud sites in two marsh ponds were converted to MAORs and samples were collected for the remaining period of study. Meiofuanal communities were numerically dominated by infaunal nematodes and harpacticoid copepods, which showed order of magnitude declines in response to MAOR addition. Shannon-Weaver diversity indices (H´) increased significantly at MAOR sites from six to 13 taxa with SIMPER analyses indicating that nematodes, copepods, tanaids, gastropods, and ostracods contributed to ≥ 95% of the cumulative dissimilarity between periods and habitats. Macrofauna communities were numerically dominated by grass shrimp (Palaemonetes pugio), blue crabs (Callinectes sapidus), and white shrimp (Litopenaeus setiferus), all of which decreased in density in response to MAOR addition. Shannon-Weaver diversity indices for macrofauna decreased at MAOR sites declining from 21 to eight species. Of the eight species present at MAOR sites only blue crabs, estuarine mud crabs (Rithropanopeus harrisii), naked gobies (Gobiosoma bosc), pinfish (Lagodon rhomboides), gulf toadfish (Opsanus beta), and sheepshead (Archosargus probatocephalus) showed increased mean densities, lengths or weights at MAOR sites. Based upon percent IRI, fish diets were dominated by insect larvae, calanoid copepods, amphipods, mysids, and polychaetes, but the relative proportions of each prey item differed among species. Statistical analyses of gut contents from each of the four fishes showed no significant effects associated with MAOR addition, but energy density analyses showed a significant effect of MAOR addition for pinfish. Energy densities were similar or higher at MAOR sites after addition and when compared between habitats. These data suggest little community level enhancement attributable to MAORs in marsh ponds. However, some specially adapted, reef-associated fishes may be able to effectively utilize MAOR-associated resources to enhance feeding or condition.
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Garner, Steven B., "Effects of mimic artificial oyster reefs on the ecology of juvenile fishes in marsh ponds: a before-after-control-impact analysis" (2012). LSU Master's Theses. 252.