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The little fish in California’s water supply: delta smelt “DRERIP” conceptual model overview

The little fish in California’s water supply: delta smelt “DRERIP” conceptual model overview. Matt Nobriga and Bruce Herbold for National Academy of Sciences OCAP Review January 25, 2010. “DRERIP”. One of several regional ecosystem restoration plans Conceptual models

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The little fish in California’s water supply: delta smelt “DRERIP” conceptual model overview

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  1. The little fish in California’s water supply: delta smelt “DRERIP” conceptual model overview Matt Nobriga and Bruce Herbold for National Academy of Sciences OCAP Review January 25, 2010

  2. “DRERIP” • One of several regional ecosystem restoration plans • Conceptual models • Support ecosystem restoration • Standardized, semi-technical statements of state of scientific understanding • Stressors operating throughout the life cycle

  3. Delta smelt life-history basics • Primarily annual

  4. Delta smelt life-history basics • Primarily annual • Migratory • “landlocked” by salinity • spawning microhabitats only assumed

  5. Delta smelt life-history basics • Primarily annual • Migratory • “landlocked” by salinity • spawning microhabitats only assumed • Generally “pelagic” • Associated with low-salinity zone

  6. Delta smelt life-history basics • Primarily annual • Migratory • “land-locked” by salinity • spawning microhabitats only assumed • Generally “pelagic” • Associated with low-salinity zone • Can move rapidly…if motivated

  7. Sacramento Sacramento River Cache Slough region Mouth of Napa River Golden Gate Bridge San Pablo Bay Suisun Bay Middle River Old River San Joaquin River SWP and CVP water export diversions Mossdale

  8. Delta smelt abundance has declined

  9. Recently declined to unprecedented low catches Data courtesy of W. Kimmerer (SFSU)

  10. Recent abundance really is low 2007-2009 indices also down here somewhere Data courtesy of W. Kimmerer (SFSU)

  11. The smelt decline is part of a pelagic system decline

  12. The fish have declined because habitat suitability has declined • Habitat metric • Flow  “X2” days in Suisun Bay ÷ Sac Valley unimpaired runoff index (water year)

  13. The fish have declined because habitat suitability has declined

  14. The fish have declined because habitat suitability has declined • Habitat metric • Flow  “X2” days in Suisun Bay ÷ Sac Valley unimpaired runoff index (water year) • Turbidity  Average sediment concentration in the Sacramento River (water year) • Food  Average density of mysid shrimp

  15. The fish have declined because habitat suitability has declined

  16. Can you be more specific about what caused the delta smelt decline?

  17. Indices of indices: survival? • FMWTt+1 ÷ TNSt Juvenile survival • Kimmerer (2008; SFEWS)

  18. Indices of indices: survival? • FMWTt+1 ÷ TNSt Juvenile survival • Kimmerer (2008; SFEWS) • TNSt+1 ÷ FMWTt Recruits per adult • This is where the population has usually been hit

  19. Higher than average Lower than average

  20. Higher than average Lower than average

  21. Conclusion • Delta smelt biology is conceptually well-understood • Quantitative life-cycle models pending • Delta smelt decline is part of a broader pelagic system decline • Driven mainly be factors occurring between maturation and early life of next generation • Conceptual support for BiOp RPAs

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