the little fish in california’s water supply: delta smelt “drerip” conceptual model overview...
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The little fish in California’s water supply: delta smelt “DRERIP” conceptual model overview
Matt Nobriga and Bruce Herboldfor
National Academy of Sciences OCAP ReviewJanuary 25, 2010
“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
Delta smelt life-history basics
• Primarily annual
Delta smelt life-history basics
• Primarily annual
• Migratory– “landlocked” by salinity– spawning microhabitats only assumed
Delta smelt life-history basics
• Primarily annual
• Migratory– “landlocked” by salinity– spawning microhabitats only assumed
• Generally “pelagic”– Associated with low-salinity zone
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
Golden Gate Bridge
Mouth of Napa River
Suisun Bay
SWP and CVP water export diversions
Sacramento
Mossdale
Old River
Middle River
San Pablo Bay
Cache Slough region
San Joaquin River
Sacramento River
0
10
20
30
40
50
60
70
80
1955 1965 1975 1985 1995 2005
Su
mm
er i
nd
ex (
un
itle
ss)
0
200
400
600
800
1000
1200
1400
1600
1800
Fal
l in
dex
(u
nit
less
)
Delta smelt abundance has declined
Recently declined to unprecedented low catches
0.01
0.1
1
10
1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Year
Mea
n c
atch
per
to
w
Data courtesy of W. Kimmerer (SFSU)
Recent abundance really is low
0.01
0.1
1
10
1960 1970 1980 1990 2000 2010
Year
Mea
n c
atch
per
to
w
2007-2009 indices also down here somewhere
Data courtesy of W. Kimmerer (SFSU)
The smelt decline is part of a pelagic system decline
0
50000
100000
150000
200000
250000
1967 1974 1981 1988 1995 2002
Year
Num
ber
colle
cted
Delta smelt Longfin smelt Striped bass Northern anchovy
The fish have declined because habitat suitability has declined
• Habitat metric
– Flow “X2” days in Suisun Bay ÷ Sac Valley unimpaired runoff index (water year)
The fish have declined because habitat suitability has declined
-6
0
6
1950 1960 1970 1980 1990 2000 2010
Water Year
Z-s
core
Flow
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
The fish have declined because habitat suitability has declined
-6
0
6
1950 1970 1990 2010
Water Year
Z-s
core
Flow Flow+sediment+food
Can you be more specific about what
caused the delta smelt decline?
Indices of indices: survival?
• FMWTt+1 ÷ TNSt Juvenile survival
– Kimmerer (2008; SFEWS)
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
-3
0
3
1968 1973 1978 1983 1988 1993 1998 2003 2008
Sta
nd
ard
ized
rat
ioSummer Survival
Higher than average
Lower than average
-3
0
3
1968 1973 1978 1983 1988 1993 1998 2003 2008
Sta
nd
ard
ized
rat
ioRecruitsPerAdult
Higher than average
Lower than average
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