Fishery Resource Utilization of a Restored Estuarine Borrow Pit: A Beneficial Use of Dredged Material Case Study
ARMY CORPS OF ENGINEERS VICKSBURG MS ENGINEER RESEARCH AND DEVELOPMENT CENTER
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Many open-water habitats that provide Essential Fish Habitat functions are also thought to be particularly susceptible to dredging project impacts. Evidence exists, however, that placement of dredged material in open-water sites can result in viable even enhanced habitat attributes and functions for fish and shellfish. For example, offshore disposal sites are often used extensively as recreational fishing areas. Dredged material can also be used to restore degraded fish habitat, such as to fill artificial pits, holes, and depressions that are scattered throughout a majority of estuaries and coastal embayments. Concerns have been voiced that pits periodically or chronically have poor water quality conditions and consequently represent degraded fish habitat. Several borrow pits in estuarine waters of New Jersey have been documented to experience low dissolved oxygen and high hydrogen sulfide concentrations, particularly during summer months. A major contributing factor to potentially poor water quality in dredged holes is hypoxia or anoxia resulting from accumulation of organic material, poor tidal flushing, and water column stratification. In 2005, the Philadelphia District of the U.S. Army Corps of Engineers partially filled a dredged hole in Barnegat Bay, New Jersey with 125,000 cubic yards of clean, sandy dredged material to raise the bottom from -11.6 m Mean Low Water MLW to an elevation of -5.5 m MLW. For monitoring purposes a nearby dredged pit served as an unrestored control. Seasonal conditions in both borrow pits were assessed in terms of water quality, benthic invertebrate community structure, fishery resource assemblage composition, and borrow pit utilization patterns. Benthic macroinvertebrates were sampled by Young grab seasonally to evaluate recruitment and community structure.
- Solid Wastes and Pollution and Control
- Water Pollution and Control