Abstract
AbstractEstuaries are among the most productive of all ecosystems and provide critical nursery habitat for many young‐of‐the‐year (age‐0) marine fish. Along the South Carolina coast, former rice field impoundments in some estuarine areas are now managed to provide habitat for waterfowl. Marine fish that enter these structures during water level manipulation become trapped and suffer high mortality rates. Because these fish cannot emigrate back to coastal waters to complete their life cycles, these impoundments appear to act as sinks for marine‐transient species. Our goal was to identify which of a set of management options would maximize export of age‐0 spot Leiostomus xanthurus from the Combahee River, South Carolina, to the coastal population. We used a structured decision‐making approach to evaluate four decision alternatives: to maintain status quo, to close all impoundments while age‐0 spot are most abundant in the river, to change the water level manipulation strategy to improve fish passage from impoundments, or to breach all impoundments. We also wanted to evaluate how impoundments and natural mortality influence the export of age‐0 spot. The optimal management decision was to change the water level manipulation strategy to increase fish passage from the impoundments. Spot export was most sensitive to juvenile settlement in the estuary and natural mortality. The results of this model can be used adaptively for impoundment management along the Combahee River and can be modified for other estuarine areas or other fish species.Received August 11, 2011; accepted February 11, 2012
Highlights
U.S Geological Survey, Georgia Cooperative Fish and Wildlife Research Unit, D
Under higher levels of spot immigration into the impoundments, we found that age-0 spot export was still most sensitive to settlement in year 4 and natural mortality in year 4
Our first objective in this study was to determine the optimal management strategy to allow for the greatest possible levels of age-0 spot export from the Combahee River estuary while taking into account stakeholder values
Summary
U.S Geological Survey, Georgia Cooperative Fish and Wildlife Research Unit, D. Spot export was most sensitive to juvenile settlement in the estuary and natural mortality The results of this model can be used adaptively for impoundment management along the Combahee River and can be modified for other estuarine areas or other fish species. In South Carolina, about 28,000 ha of coastal marsh (approximately 14% of total marsh area) are currently impounded, with an additional 30,000 ha of abandoned impoundments subject to tidal inundation (Tiner 1977; DeVoe et al 1987; Kelley 1999) Most of these impoundments are managed to provide food and habitat for migratory waterfowl (DeVoe et al 1987; McGovern and Wenner 1990). Many transient species, including the spot Leiostomus xanthurus, Atlantic croaker Micropogonias undulatus, southern flounder Paralichthys lethostigma, tarpon Megalops atlanticus, and ladyfish Elops saurus, have been observed in South Carolina impoundments (Wenner et al 1986; Robinson 2011)
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