Lower Chehalis River and Surge Plain Fish Use Assessment Report
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LOWER CHEHALIS RIVER AND SURGE PLAIN FISH USE ASSESSMENT May, 2015 James Fletcher, Todd Sandell and Andrew McAninch Prepared for: The Rose Foundation Table of Contents 1.0. INTRODUCTION ................................................................................................... 3 2.0. BACKGROUND AND PURPOSE ............................................................................. 3 2.1. SEA LEVEL RISE IN GRAYS HARBOR ESTUARY ................................................................. 3 2.2. SPECIFIC OBJECTIVES ................................................................................................................ 5 2.3. SAMPLING GOALS ....................................................................................................................... 5 3.0. STUDY AREA ........................................................................................................ 6 3.1. SALMON STOCKS .......................................................................................................................... 6 3.2. CHEHALIS RIVER SURGE PLAIN AND LOWER RIVER ...................................................... 7 4.0. FIELD SAMPLING METHODOLOGY ....................................................................... 9 4.1. FISH DATA .................................................................................................................................... 10 4.2. DATA RECORDING/WATER QUALITY MEASURES .......................................................... 10 4.3. AGE CLASS ASSIGNMENTS ..................................................................................................... 11 4.4. CATCH CALCULATIONS/ FISH DENSITIES ......................................................................... 11 5.0. RESULTS ............................................................................................................ 12 5.1. CATCH TOTALS ......................................................................................................................... 12 5.2. HATCHERY RECOVERIES ...................................................................................................... 15 5.3. SALMON GROWTH/AGE CLASS ............................................................................................. 15 5.3.1. Chinook Salmon ......................................................................................................................... 16 5.3.2. Coho Salmon .............................................................................................................................. 18 5.4. SALMON DISTRIBUTION AND TIMING (DENSITIES) ................................................... 19 5.4.1. Chinook salmon ......................................................................................................................... 19 5.4.2. Coho salmon .............................................................................................................................. 20 5.4.3. Chum salmon ............................................................................................................................. 20 6.0 SUMMARY ......................................................................................................... 24 ACKNOWLEDGEMENTS......................................................................................................... 27 REFERENCES......................................................................................................................... 27 APPENDIX 1. Chinook and Coho Salmon Fork Length Age Class Cutoffs (mm) ......................... 30 APPENDIX 2. Sampling Sites ................................................................................................ 30 APPENDIX 3. Stream Flow.................................................................................................... 31 APPENDIX 4. Summary of Factors Effecting Fish Abundance and Presence in Grays Harbor 2011 – 2013 ......................................................................................................................... 32 APPENDIX 5. Water Temperature by Site ............................................................................. 33 Lower Chehalis River Juvenile Fish Use Assessment, 2015 Wild Fish Conservancy Page 2 1.0. INTRODUCTION The Chehalis River and Estuary are part of the range of habitats that salmon originating from the Chehalis River and its tributaries use during their life cycle. As such, juvenile salmon originating from the extensive network of rivers and streams in Water Resource Inventory Areas (WRIAs) 22 and 23 must all use some portion of the freshwater, estuarine and nearshore habitats in the Grays Harbor as they emigrate to the ocean. Estuarine environments are extremely productive habitats and provide four main functions for juvenile salmon: growth and rearing, physiological transition from freshwater to saltwater, migratory pathways to the ocean, and predator avoidance (Simenstad et al. 1982). Estuarine habitats vary in their ability to support these functions as a result of natural and anthropogenic variability in the qualities of the habitat. Understanding how well the lower Chehalis River and the transition zones to estuarine habitats support these functions is a critical component in the development of a salmon restoration strategy for the entire basin. 2.0. BACKGROUND AND PURPOSE In 2011 Wild Fish Conservancy began research to understand how the estuarine habitats in Grays Harbor are utilized by emigrating juvenile salmon (Grays Harbor Juvenile Fish Use Assessment, Sandell et al. 2014). Understanding the relationship between salmon and their habitats is the foundation for developing a restoration strategy to ensure the viability and persistence of salmon populations. Our objectives were to document how fish utilize the variety of estuarine habitats associated with Grays Harbor as they emigrate to the sea, or, in some cases, rear in the estuary for up to a year. This work also led us to seek support from the Rose Foundation to investigate the lower mainstem Chehalis River, to better understand the timing of emigration, the habitats most utilized by juvenile salmon, and the environmental variables found in the lower river. 2.1. SEA LEVEL RISE IN GRAYS HARBOR ESTUARY In 2012, concerned with the potential for sea level rise to severely alter habitat availability in the Grays Harbor estuary as well as to undermine many of the habitat restoration projects planned for the area, Wild Fish Conservancy conducted a modeling Lower Chehalis River Juvenile Fish Use Assessment, 2015 Wild Fish Conservancy Page 3 of climate change in the Chehalis Basin (Sandell & McAninch, 2013). Using the Sea Level Affecting Marshes Model (SLAMM), we analyzed the estuary with regard to sea level rise (SLR) under different climate change scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC). The model predicted rapid changes in the upper estuary, specifically the freshwater tidal Surge Plain (Figure 1), “[which will] transition from forested tidal swamp to irregularly flooded marsh by 2025 even in the most conservative scenario; the net loss of forested area is predicted to be severe (~97% for the estuary as a whole).” The vast majority of forested area in the estuary is found in the Surge Plain, where the lower Chehalis River becomes tidally influenced. The predicted changes in the present day Surge Plain, due in part to the encroachment of a salt water “wedge” that may kill the large trees and undermine the stability of the many off- channel sloughs in the area, could dramatically alter the habitat and migration corridor utilized by juvenile salmon. For this reason, we are now focused on understanding where the future Surge Plain is likely to occur and how juvenile salmon are currently utilizing this area, so that conservation managers can make effective planning decisions that addresses climate change well into the future. Figure 1. Mean High Water levels for the Surge Plain under 5 sea-level rise scenarios (0.59, 0.75, 1.0, 1.25, and 2.0 meter rise);calculated with a DEM processed to correct for high water levels during some of the dates LiDAR was acquired. Lower Chehalis River Juvenile Fish Use Assessment, 2015 Wild Fish Conservancy Page 4 2.2. SPECIFIC OBJECTIVES The Lower Chehalis River and Surge Plain Fish Use Assessment was developed as a pilot study, conducted by the Wild Fish Conservancy with funding provided by the Rose Foundation. The primary goals were to anticipate the location and extent of the future Surge Plain and to identify the key habitat areas utilized by juvenile salmon and other fishes. The project had four specific objectives at the outset: 1. Estimate the future head of tidal intrusion and map the habitats of the lower river using 2013 LiDAR data. (Accomplished in July, 2014) 2. Determine the abundance, distribution, emigration timing and habitat preferences of juvenile salmonids in the Surge Plain and lower Chehalis River. Meeting this objective also establishes the presence of these fish at locations in the lower river, a prerequisite for land acquisition for conservation or conservation easements. 3. Understand which physical variables (flow rate, dissolved oxygen, temperature, salinity) best predict the distribution of Chinook, coho, and chum salmon, and which habitat types are of the highest priority. 4. Integrate this knowledge into the Grays Harbor Estuary Salmonid Conservation Plan, which identifies specific restoration and conservation opportunities in the estuary,