Monitoring a Nearshore Beneficial Use Site: Application of a Benthic Sled and Video Annotation

The U.S. Army Corps of Engineers (USACE) Portland Districts (NWP) maintains safe and navigable waterways in Oregon through a variety of dredging projects, including channel deepening, and dredging sandbars. Placement of dredged sediment occurs at preselected, specific geographic areas categorized as nearshore beneficial use sites. Beneficial use sites are commonly monitored before, during, and after disposal, to evaluate dredge management practices and to avoid potentially adverse effects to the marine environment.

Ecological monitoring focuses on the survey of fish and epibenthic invertebrate species distribution and abundance. Surveys are conducted within, and outside the disposal area to assess changes in population or community structure, and to establish diversity indices for comparisons over time. A commonly used survey method to accomplish this goal is a bottom trawl survey, whereby a net is dragged along a preselected part of the ocean floor for a specific time and distance. The net is then retrieved onto the boat where the aquatic life can be more closely examined and the taxa are sorted. Traditional trawl surveys are labor and resource intensive, highlighting the opportunity to improve alternative “passive” survey methods.