Water quality and acoustic investigation of shortnose sturgeon habitat in the Savannah River
Knight, Laura Lynn
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The Savannah River Estuary (SRE) has historically been challenged to meet water resource demands for multiple, sometimes opposing user groups, such as the global economic engine of the Savannah Port, environmental advocates and the commercial fishing interests within the same stretch of river. Resolution of this conflict is exacerbated when the SRE’s most imperiled fish, the endangered shortnose sturgeon (SNS) (Acipencer brevirostrum), lacks economic incentives for preservation. Unfortunately, shortnosed sturgeon have no residual commercial value from when they were over-fished to near extinction in the late 1960’s for their prized roe, placing them as the first listed species of the Endangered Species Act. Given the dwindling SNS numbers, recovery requires a plan to protect this species purely for holistic concerns over diminishing bio-diversity within the estuary. The solution, therefore, is necessarily a blend of science and policy to delineate the most threatened habitat where this species is known to exist. Primary shortnose sturgeon habitat in the SRE, however, is located within the busiest section of the port. This study investigates identified SNS habitat to delineate and draft protective recommendations for the most at risk portions of the lower SRE, plagued by both poor water quality (low DO, high temperature and salinity) and degraded physical habitat. Water quality sampling, mid-range side-scan sonar, high-frequency DIDSON sonar and stakeholder interviews were used to map the key areas of concern. These data reflect the need to investigate and preserve unique habitat features like the single remaining fish hole located in the freshwater-tidal interface. This fish hole provides protection for many species against salinity spikes and thermal stress within the SRE Middle River. The Georgia Port Authority and United States Army Corps of Engineers plan to expand the Kings Island Turning Basin (KITB) near this unique/rare habitat (the Middle River fish hole). Unmitigated, this expansion may alter river flows, destroying fish hole structural integrity or silting in the rich organic debris lining the bottom. This study employs ArcMap to indicate the most severely degraded habitat, potentially aiding in the prioritization of alternatives identified through the NEPA process of the Savannah Harbor Expansion Project.