Dungeness crab and razor clam surveys at sites near Grays Harbor, Washington, and at Willapa Bay bar entrance, September 1993

摘要

Grays Harbor and Willapa Bay are shallow embayments on the outer coast of Washington state. The US Army Corps of Engineers, Seattle District is responsible for maintenance of navigational channels in these areas, a task that requires routine dredging of deposited sediments. Dredged sediments are normally transported to designated sites for disposal. At the entrance to Grays Harbor, severe shoreline erosion has occurred. To slow erosional processes and prevent a breach at the base of the South Jetty, the USACE proposed the beneficial use of dredged materials from the bar and entrance reaches of Grays Harbor. Dredged materials deposited as sediment berms just offshore of South Beach, to the south of the jetty base, and at Half Moon Bay, to the north and east of the jetty base, could mitigate erosional processes in two ways: (1) by providing nearshore sacrificial material and a sediment supply for accretion on the shores, and (2) by tripping larger waves further offshore from the beaches. Battelle Marine Sciences Laboratory was contracted to conduct surveys at four sites in September 1993. The primary objective of this work was to determine the density of Dungeness crab at sites associated with dredging activities or dredged-materials disposal. A related objective was to assess the density of juvenile razor clams at the South Beach site, the only site in this study with potential to be an important recruitment area for juvenile razor clams.