Fish abundances in shoreline habitats and submerged aquatic vegetation in a tidal freshwater embayment of the Potomac River |
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Authors: | Email author" target="_blank">Richard?T?KrausEmail author R?Christian?Jones |
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Institution: | (1) Department of Environmental Science, Potomac Environmental Research and Education Center, George Mason University, 4400 University Drive, MS 5F2, Fairfax, VA 22030, USA;(2) Present address: US Geological Survey, Great Lakes Science Center, Lake Erie Biological Station, 6100 Columbus Avenue, Sandusky, OH 44870, USA |
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Abstract: | Submerged aquatic vegetation (SAV) is considered an important habitat for juvenile and small forage fish species, but many
long-term recruitment surveys do not effectively monitor fish communities in SAV. To better understand the impact of recent
large increases of SAV on the fish community in tidal freshwater reaches of the Potomac River, we compared traditional seine
sampling from shore with drop ring sampling of SAV beds (primarily Hydrilla) in a shallow water (depths, <1.5 m) embayment,
Gunston Cove. To accomplish this, we developed species-specific catch efficiency values for the seine gear and calculated
area-based density in both shoreline and SAV habitats in late summer of three different years (2007, 2008, and 2009). For
the dominant species (Fundulus diaphanus, Lepomis macrochirus, Etheostoma olmstedi, Morone americana, Lepomis gibbosus, and Fundulus heteroclitus), density was nearly always higher in SAV, but overall, species richness was highest in shoreline habitats sampled with seines.
Although historical monitoring of fish in Gunston Cove (and throughout Chesapeake Bay) is based upon seine sampling (and trawl
sampling in deeper areas), the high densities of fish and larger areal extent of SAV indicated that complementary sampling
of SAV habitats would produce more accurate trends in abundances of common species. Because drop ring samples cover much less
area than seines and may miss rare species, a combination of methods that includes seine sampling is needed for biodiversity
assessment. The resurgence of SAV in tidal freshwater signifies improving water quality, and methods we evaluated here support
improved inferences about population trends and fish community structure as indicators of ecosystem condition. |
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