Issue
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Resource agencies have
concerns that placement of dredged material containing more than a few percent of fine-grained
sediments in nearshore coastal
waters could detrimentally affect fishery resources. Potential impacts include loss of critical nursery habitat due to the presence of
turbidity plumes, blockage of migratory corridors, and effects of suspended sediments on
growth and survival of larval and juvenile fish and
shellfish. Also, sensitive habitats can potentially be damaged in the short term when dredged material is placed in the active zone, or
in the long term as fill material adjusts to the shore face. The validity of these concerns
remains uncertain, but these issues arise frequently
and must be addressed during the interagency coordination process. For resource agencies to consent to nearshore placement of
dredged material as a viable management technique, it must first be clearly demonstrated that
potential adverse impacts can be minimized or
eliminated.
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Research/Objectives
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The objective of this research is to document the responses of fishery resources to dredging-induced turbidity plumes
and sediment resuspension in the nearshore zone. The research is measuring effects of
project alterations on growth and survival of target
species. Additionally, guidance on siting, timing, and a disposal mode that would minimize disturbance of nearshore habitats critical
to fishery resources is being developed. Surveys of fish and shellfish occupation of
nearshore habitats subject to dredged-material placement
are being used to establish the functions and relative importance of these habitats to resident and transient fishery resources. These
surveys, in conjunction with monitoring of potentially elevated turbidity and suspended
sediment fields associated with nearshore placement,
are being used to detect changes in use of these habitats. Specific concerns are being addressed by laboratory and/or field
investigations of life-history stages of key taxa to determine thresholds, types, and magnitudes of
responses to conditions induced by nearshore placement
practices. Recommendations and guidance on how to optimally protect biological resources during the course of nearshore placement
projects will be based on the results of all studies.
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