Estuarine wetlands and floodplains are often credited as a source of enhanced productivity compared with main-channel habitat because of their enriched habitat complexity. In the lower Columbia River and Estuary (LCRE), work at select locations has been completedresearch assessing the diets of juvenile Chinook salmonids and characterizing potential prey pools has, to increase understanding of the relationship between salmonid foraging ecology and habitat capacity. However, the Expert Regional Technical Group of the Columbia Estuary Ecosystem Restoration Program (CEERP) has determined that little research has addressed whether large-wood retention contributes to productivity in estuaries, as has been assessed in non-tidal systems. Further outstanding questions concern differences between large wood structures such as size, complexity, decay, surface texture, tree species, and surface vegetation. Research on juvenile salmon pPrey pools most commonly sampled in the LCRE are have included wetland channels, off-channels, and mainstem areas and have targeted micro habitats within these locations (e.g. benthic habitats, water surfaceneuston, and marsh vegetation)fallout, and emergence samples, but studies to date have not addressed the role of structures such as large wood as a medium for colonization within tidal environments. To address these data gaps and inform CEERP planners and managers, the goal of this large wood estuarine experimental design specifically focuses onis to determine the roles of large wood in tidal wetland channels of the LCRE relative to habitat functions of benefit to juvenile salmon (e.g., refuge, prey production). The objectives of this research include determining the response of biological and environmental conditions in channels with large wood structures compared to channels without.  

We have developed the following hypotheses to address research goals and objectives: 

Biological Response Variables: 

1. Salmon abundance in treatment channels will be greater as beach seining events get nearer to the LWDthan abundance in control channels. 

2. Fish assemblages will be more abundant and diverse as beach seining events get nearer to the LWDin channels with LWD compared to channels without wood structure.  

3. Invertebrate abundance and diversity will be higher in channels withproximity to LWD compared to channelsareas without wood structure.  

4. Invertebrate biomass and energy densities in proximity to LWDtreatment channels will be higher than those measured in control channelsareas1. 

Environmental Response Variables: 

1. The density of wood will have a direct, inverse relationship to water temperature. Water temperature in treatment channels will be less than water temperature in control channels. 

2. The density of wood will have a direct, inverse relationship to water velocity. Water velocity in treatment channels will be lower than water velocity in control channels. 

The large wood research project will occur at the newly created South Tongue Point restoration site (see Appendix 2 for an image of the site and vicinity). The research will focus on collecting data from three channel networks (Figure 1). Each network will have one treatment channel, which includes LWD structures, and one control channel (no LWD). Sampling would occur monthly during March – May to coincide with juvenile salmon outmigration. The time horizon to complete monitoring for the large wood study is anticipated to be 4-5 years starting with construction, and ideally longer to allow for food web development.