Lower Columbia River Estuary

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Lower Columbia River Estuary

• Mapping Subtidal Large Woody Debris and Other
  Habitat Features Relative to Fish Distribution
• Battelle Pacific Northwest Division
• Lower Columbia River Estuary Partnership (LCREP)

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Objectives

• Map shallow subtidal habitat features (i.e.,
  large woody debris (LWD))
• Merge data with GIS habitat classification maps
  of wetland and intertidal zones
• Relate shallow subtidal habitat features to
  patterns of fish density and distribution
• Apply innovative fish detection methods to assess
  salmonid use of the habitat features

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Subbasin Need Assess the extent and ecological
significance of various estuarine habitats,
including LWD.
Photo courtesy of L. Weitkamp, NMFS
Limiting Factor Addressed Reduced amount of LWD
in streams, sloughs, and bays of the Lower
Columbia River Estuary.
Battelle Pacific Northwest Division
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• Large Woody Debris Provides

• Habitat complexity
• Juvenile salmon refugia
• Augmentation of epibenthic prey

Photo courtesy of LTER

• Reduced Levels of LWD due to
• Logging activities
• Suppression of water flow with reduced flooding
• Removal, meant to prevent fouling of nets

Battelle Pacific Northwest Division
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Study Area (Suggested Site Selection)

• Shallow subtidal habitat
• in Cathlamet Bay
• Main channel
• Channel margin
• Tidal slough
• Battelle and other interested agencies will
  coordinate to select appropriate sites.

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Study Design

• YEAR 1
• Project Planning/Design
• Develop sampling design and refine site selection
  for pilot scale mapping effort
• Construction/Implementation
• Mobilize and test side-scan equipment
• Conduct pilot scale side scan sonar mapping in
  Cathlamet Bay
• Conduct video camera surveys
• Analyze side scan sonar images and classify large
  woody debris
• Assess sampling methods and modify for Year 2

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Study Design, continued

• Years 2 and 3 will take an adaptive approach,
  based on previous results.
• YEAR 2
• Repeat side scan sonar mapping and add additional
  sites
• Mobilize Dual-frequency Identification Sonar
  (DIDSON) acoustic camera and underwater video to
  quantify fish density and behavior at sites with
  LWD
• YEAR 3
• Collect 2nd year of DIDSON and underwater video
  data
• Re-map LWD (?)
• Spatially link patterns of fish habitat use and
  abundance to distributions of LWD in a GIS
  framework

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Side Scan Sonar

• Towed underwater system
• Geo-referenced mosaics
• High-resolution benthic habitat and substrate
  features

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Side Scan Sonar Large Woody Debris
Large logs and other debris

• Large woody debris pile, dock, piling, and boulder

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Dual-frequency Identification Sonar (DIDSON)
Acoustic Camera
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Dual-frequency Identification Sonar (DIDSON)
Acoustic Camera
One fish (30 cm) swimming near large woody debris
Two 50-cm fish and the seabed
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Expected Results

• Production of a series of GIS maps depicting
  distribution of LWD relative to bottom features
  and other relevant geo-referenced data
• Merge data with GIS habitat classification maps
  of wetland and intertidal zones, currently being
  developed from Compact Airborne Spectrographic
  Imager (CASI) hyperspectral imagery data
• Physical conditions under which LWD is most
  commonly found
• Variation in location and amount of LWD on annual
  basis
• Assessment of importance of subtidal LWD as
  habitat for juvenile salmonids

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