Ed Casillas NWFSC, Seattle, WA (Contributors – UW, OSU, OHSU, WDFW, PSU, COE, BPA)

1. Role of Tidal Saltwater Habitats for Juvenile Salmonids(Myths vs Reality in the Columbia River Estuary) Ed Casillas NWFSC, Seattle, WA (Contributors – UW, OSU, OHSU, WDFW, PSU, COE, BPA)

2. Role of Estuaries • Historical Drivers – Production, abundance, mortality • Conduit – Connect upstream spawning and rearing areas to ocean habitat • Transition to saltwater Current Drivers - Population viability & resilience, habitats salmon use and need • Productive feeding area • Refuge from predators

3. Marine Mixing Tidal fresh Myth - Juvenile salmon use the estuary for a short period of time (as individuals and as populations) Marine Tidal Fresh Mixing Reality – Juvenile salmon present in the estuary year around

4. Myth – Salmon populations predominantly use the subyearling and yearling strategy to succeed Reality - All ESUs use a variety of juvenile life history strategies to succeed Subyearlings/Yearlings 100-200 mm Alevins Fry – distributes throughout the river, estuary and ocean Fingerlings – rears near spawning area for 1-2 months, then distributes throughout river, estuary, and ocean Subyearling/Yearling – rears in river, then migrates to the ocean Size seen in the ocean, composed of juveniles using fry, fingerling, subyearling, and yearling strategy Fingerlings 60-90mm Fry 40-60mm

5. Fry a Dominant Strategy in the Columbia River Estuary Monthly Fry Proportion >50% of juvenile enter estuary at < 60mm Fry Mean Percent Month

6. Fry Strategy Used by Many Chinook ESUs in the Columbia River

7. Myth - Juveniles only use the estuary to transit to the ocean Reality – Juveniles grow in the estuary

8. Corollary – If juveniles grow in the estuary, they then must reside in the estuary Point Adams Beach 2004 May-Aug Estuary habitat use and residency is size related 140 120 y = -0.9705x + 110.91 100 2 R = 0.5172 Residency (days) 80 • Juveniles enter the estuary over a wide range of sizes • Residence time decreases with size at estuary entry 60 40 20 0 0 20 40 60 80 100 120 Back Calculated Fork Length at Estuary Entry (mm) Data from Lance Campbell

9. Chinook Length Frequency in Wetland Channels 2004 April n = 155 May n = 122 Scrub-Shrub Frequency of Occurrence June n = 39 Forested July n = 19 Fork Length (mm) Which Habitats are Used by Juvenile Salmon Emergent • Small size classes frequent shallow, nearshore and wetland habitats • Few juveniles > 90 mm enter or remain in interior marsh channels

10. Myth – Juvenile salmon feed primarily on benthic aquatic organisms Reality – Juvenile salmon feed dominantly on terrestrially derived insects 60-90mm 40-80mm 70-120mm

11. Myth – The Columbia River Estuary Benefits Lower River stocks only Reality - Most all ESUs use estuarine habitats -Stock composition varies through the year

12. Myth – Only subyearling from lower river stocks use wetland habitats Reality – Subyearlings and yearlings from interior basin also use wetland shallow water habitats CREST Pit tag detector array in secondary wetland channel 2009 Detections Lower Columbia River Chinook salmon, N=32 Lower Columbia River coho salmon, N=5 Snake River fall Chinook salmon, N=1 Snake River spring Chinook salmon, N=1 Snake River summer steelhead, N=3

13. If estuaries provide opportunity for diversification of life history strategies and diversity is an attribute of healthy salmon populations, how does the Columbia River system fare? Jan Mar May Jul Sep Nov Jan Mar May Jul Fry Contemporary Fingerling Natal / Fluvial Rearing Yearling Relative Abundance Jan Mar May Jul Sep Nov Jan Mar May Jul Estimated changes in the relative proportions of juvenile salmon life histories From Burke, 2005. Data from Rich (1920) & Dawley et al. (1985) Simplication of life histories may undermine resilience and recovery of Columbia River Chinook salmon

14. Can Salmon Life History Diversity be Restored? Estuarine restoration, life history strategies, and adult returns; the Salmon River story

15. Can Life History Diversity be Restored? Lower estuary 100 100 Mid estuary 2000 1975 Upper estuary 80 80 Lower estuary Mid estuary 60 60 Upper estuary 75' seine (1977) Upper estuary 125' seine (1977) 40 40 20 20 0 0 100 100 1976 2001 80 80 60 60 CPUE (number/seine haul) CPUE (number/seine haul) 40 40 20 20 0 0 100 100 1977 2002 80 80 60 60 40 40 20 20 0 0 Mar May Jul Sep Nov Mar May Jul Sep Nov Before Estuary Restoration After Estuary Restoration • Life history diversity has expanded with increased wetland opportunity

16. Myth – Estuarine restoration does not affect adult returns Reality – Recovered life history strategies contribute to adult returns Size at Estuary Entry for Juveniles at Mouth (BY 2001 & 02) Emergent Fry < 45mm 7% Spring (MAM) 47 – 64 mm 10% Summer (JJA) 55 – 96 mm 77% Fall (SON) 97 – 109 mm 6% Size at Estuary Entry for Adults (2004 RY; n=145) Emergent Fry < 45 mm Spring (MAM) 47-64 mm Summer (JJA) 65-96 mm Fall (SON) 97-110 mm 17% 14% 57% 12%

17. Summary – Estuary as Salmon Habitat • Based on distribution preferences and growth characteristics, estuary a habitat for smaller juvenile salmon to grow • Shallow water, low velocity, and low salinity surface environments with associated wetland vegetation are features that define habitat • Diverse distribution of habitat a surrogate for diversity and spatial structure of salmon population • All juveniles benefit from estuary habitat through food webs and predator refuge • Preservation and restoration of shallow water, low velocity, and low salinity environments an important strategy for recovery of salmon and to mitigate for anthropogenic modifications