Lower Columbia River Estuary

1. 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)

2. 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

3. 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

4. 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

5. 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.

6. 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

7. 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

8. Towed underwater system Geo-referenced mosaics High-resolution benthic habitat and substrate features 0 100 meters Side Scan Sonar

9. Large woody debris pile, dock, piling, and boulder Side Scan Sonar: Large Woody Debris Large logs and other debris

10. Dual-frequency Identification Sonar (DIDSON) Acoustic Camera

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

12. 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