1. 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

2. 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!

3. 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

4. Premise II
Low
flow X2 X2
Physical
habitat
increases
High
flow

5. 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

6. 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

7. 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

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

9. TRIM3D Calibration
January 1998
Salinity
March 1998

10. 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

11. 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

12. Example Habitat Curves
Data from Bay Study Midwater Trawl

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

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

15. 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

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

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

19. 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

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