Variation of Physical Habitat for Estuarine Fish with Freshwater Flow Wim Kimmerer Romberg Tiburon Center for Environmental Studies San Francisco State University Ed Gross Mike MacWilliams

Premise I Abundance or survival of several estuarine-dependent species increases with freshwater flow We want to know the mechanisms Refine X2 standards Improve management Change in Delta configuration Not yet trumped by POD!

Updated Fish-X2 Relationships No change in slopes, lower in some POD years Decline after 1987 except delta smelt (1981) and striped bass (1995) Kimmerer 2002 MEPS 243: 39

Premise II Low flow X2 X2 Physical habitat increases High flow

Premise III: Classes of Mechanism F: Food supply increases with flow T: Rates of transport increase with flow Q: Water quality improves with flow H: Area or volume of habitat increases with flow

Premise III: Classes of Mechanism F: Food supply increases with flow T: Rates of transport increase with flow Q: Water quality improves with flow H: Area or volume of habitat increases with flow

Premise IV: Habitat Characteristics “Habitat” = Volume in Salinity (and Depth) ranges (Abundance  Habitat volume) Not: Turbidity Physical or hydrodynamic complexity Connection to shore or marsh features Predator refuge

TRIM3D Model Grid: Example at Intermediate Flow Water Column Mean Salinity

TRIM3D Calibration January 1998 Salinity March 1998

Volume in depth and salinity ranges TRIM 3D Output Volume in depth and salinity ranges Label flows in yellow >0.2 0.1 0.01 0.001 Volume km3 Numbers give flow, m3 s-1

Example Habitat Curves TRIM 3D: 5 Flows Color = Volume Weighting Determined from field data: 4 sampling programs 5,000 to 13,000 data points included Generalized Additive Models Fit to Salinity + Depth (Otter Trawl) or Salinity (all others) Abundance and Frequency data

Example Habitat Curves Data from Bay Study Midwater Trawl

Delta Smelt Compare Slopes: Habitat Index (catch) Habitat Index (% Freq) Abundance-X2 Change graph upper left – raw data with GAM curve

Bottom Line X2 - Abundance X2 - Habitat (Catch) X2 - Habitat (% Freq.) Bay Shrimp Starry Flounder Pacific Herring Northern Anchovy Amer. Shad

Funding from the CALFED Ecosystem Restoration Program Summary Habitat variability Consistent with some fish-X2 relationships (doesn’t mean it is the explanation) Inconsistent for other species Other possibilities? Funding from the CALFED Ecosystem Restoration Program

Premise IV: Habitat Characteristics “Habitat” = Volume in Salinity (and Depth) ranges (Abundance  Habitat volume)

Example Habitat Curves TRIM 3D: 5 Flows Color = Volume

Example Habitat Curves Determined from field data: 4 sampling programs 5,000 to 13,000 data points included Generalized Additive Models Fit to Salinity + Depth (Otter Trawl) or Salinity (all others) Abundance and Frequency data

Bottom Line X2 - Abundance X2 - Habitat (Catch) X2 - Habitat (% Freq.) Bay Shrimp Starry Flounder Pacific Herring Northern Anchovy Amer. Shad