Date of Award

4-30-2018

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

First Advisor

Keith R. Walters

Second Advisor

Dennis M. Allen

Third Advisor

Charles Martin

Additional Advisors

Robert F. Young

Abstract

Oyster reefs are essential fish habitat and a worldwide loss of reefs has the potential to negatively affect reef-associated nekton populations. Along the 100 km Myrtle Beach, SC shoreline, oyster reefs ostensibly have disappeared within swash tidal creeks, which are anthropogenically altered estuarine systems that drain into the coastal ocean directly over shoreline beaches. To address oyster reef losses, a series of shell bag reefs were constructed within multiple swash tidal creeks. Reefs also were constructed in tidal creeks associated with estuaries directly connected to the ocean by an inlet. The purpose of this study was to compare nekton usage of newly constructed restored oyster reefs, prior to significant spat settlement, between the two creek systems. Baited minnow traps, gill nets, and pull traps were used to sample nekton on or next to restored reefs. Limited natural reefs and variable water quality within swash creeks suggested that reef associated nekton would be different in swash than in inlet creeks. Small fishes (< 120 mm standard length, ≈ 97% Pinfish and Mummichog) were captured in greater number and condition from restored swash reefs than inlet reefs. Decapod abundance and grass shrimp condition trended inversely with small fish abundance and condition, suggesting inlet reefs may provide decapods with higher quality habitat. Larger, piscivorous fishes were captured more frequently from inlet than swash creeks, but they were likely not reliant on restored reef substrate. Nekton numbers were also dependent on tidal elevation (intertidal/subtidal) and diel stage (day/night). Fishes captured by intertidal traps directly over restored reefs were smaller on average than those captured by subtidal traps just off the reefs, suggesting shell bags provided nursery habitat even before the restoration site became a more established reef with the settlement of spat. Rarefied richness of both fishes and decapods was greatest at inlet creeks. A habitat abundance study was conducted after a residency period of one year to test trap efficacy and attraction of nekton to restored reefs compared to natural reefs and mudflat substrate. Catches of small fishes at restored reefs failed to converge with natural reef catches, but were still greater than from mudflats. Decapods were most abundant at restored reefs, suggesting new reefs provide them with excellent short-term habitat. Piscivore density was greatest over mudflat substrate, indicating their indifference to early reefs. Nekton colonization of constructed oyster reefs occurred rapidly (<6 months) in both inlet and swash tidal creeks before any appreciable new recruitment and growth of oysters. The abundance and richness of reef nekton reflected overall differences in the sizes of nekton populations between inlet and swash creeks. Even during early stages of an oyster reef restoration project, constructed shell bag reefs provide attractive habitat for many fishes and decapods critical to estuarine food webs.

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