Importance of Habitat in salmon declines and recovery Ray Hilborn School of Aquatic and Fishery...
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Transcript of Importance of Habitat in salmon declines and recovery Ray Hilborn School of Aquatic and Fishery...
Importance of Habitat in salmon declines and recovery
Ray HilbornSchool of Aquatic and Fishery Sciences
UW
What is wrong with salmon?The 4-H’s
• Harvest– We take too many
• Habitat– We degrade their streams
• Hydroelectric– We block passage, turn rivers into lakes
• Hatcheries– We try to “mitigate” for habitat loss by artificial
production
Structure of talk
• Trends in abundance– How bad is the problem
• Ocean conditions – the BIG driver
• Hydroelectric
• Harvest
• Hatcheries
• Habitat
Myth IWe are running out of wild
salmonThe “truth”: there are nearly as many wild salmon in western North America now as any time since Europeans arrived
But: this due primarily to Alaska, and in the Lower 48 many stocks are extinct and most are well below historical levels
0
10
20
30
40
50
1893
1899
1905
1911
1917
1923
1929
1935
1941
1947
1953
1959
1965
1971
1977
1983
1989
1995
Cat
ch i
n m
illi
on
s o
f fi
sh
Bristol Bay wild sockeye
1970 1980 1990 20001988199019921994199619981987 1989 1991 1993
200
400
600
800
Run
Size
Puget Sound Coho Wild Returns
1988 1991 1994
20
60
100
1988 1990 1992 1994 1996 1998 2000 1960 1970 1980 1990 2000
400
300
200
100
Ru
n
Siz
e
Year
A B C
D E F
Chinook salmon past Bonneville Dam
Myth IIThe ocean is big, unlimited and salmon abundance is driven by
freshwater and habitat
The “truth”: most large scale variation in salmon abundance is driven by ocean changes
But: this only means it is harder to detect anthropogenic impacts
Lake Nerka, SW Alaska
0
10
20
30
2 4 6 8 10
Sediment 15N (‰)
Sal
mon
den
sity
(1
00
0s/
km2)
Mixing model
referencelakes
sockeye
Historical sockeye population dynamics
4
5
6
7
8
Sed
imen
t 15
N(‰
)
1750 1850 19501800 1900 2000
Sediment chemistry
1750 1850 19501800 1900 20000
4
8
12
Year
Sockeye population
Sal
mon
den
sity
(1
00
0s/
km2)
Schindler and Leavitt (2001)
Lake Nerka, SW Alaska
Historical sockeye population dynamics
1750 1850 19501800 1900 20000
4
8
12
Year
Sal
mon
den
sity
(1
000s
/km
2 )
+ fishery catch
escapement
Schindler and Leavitt (2001)
0
4
8
12S
ocke
ye(1
000s
/km
2)
1750 1800 1850 1900 1950 2000
Sockeye density
Effects of sockeye population on phytoplankton production
0
4
8
12
Dia
toxa
nthi
n(n
mol
/g)
Year
0
2
4
6
Lute
in-z
eaxa
nth
in(n
mol
/g)
1750 1800 1850 1900 1950 2000
Algal pigments in lake
sediments
Schindler and Leavitt (2001)
0% 2% 4% 6% 8% 0% 1% 2% 0% 1% 2%
Survival rate by Realm
Arctic
SE Alaska
Coastal BC
Georgia Strait
Puget Sound
Coastal Washington
Columbia Basin
Coastal Oregon
California
CohoFall
chinookSpringchinook
Avg survival rate
Coho survival rate by Domain
Release year
Survivalrate
0%
3%
6%
9%
12%
15%
72 74 76 78 80 82 84 86 88 90 92 94 96 98
Alaska and YukonBC and Puget SoundCoastal WaOrCaColumbia basin
Fall chinook survival rate by Domain
Release year
Survivalrate
0%
1%
2%
3%
4%
5%
72 74 76 78 80 82 84 86 88 90 92 94 96
BC and Puget SoundCoastal WaOrCa
Columbia basin
Spring chinook survival rate by Domain
Release year
Survivalrate
0%
1%
2%
3%
4%
5%
6%
7%
72 74 76 78 80 82 84 86 88 90 92 94 96
Alaska and Yukon
BC and Puget Sound
Coastal WaOrCa
Columbia basin
Myth IIIThe decline of NW salmon is due
to damsThe “truth”: systems without dams have had similar trends
But: clearly dams are not good for salmon and are part of the problem
Chinook survival by river segment
Fall chinook Spring chinook Fall chinook
Columbia Columbia Fraser
Su
rviv
al
rate
100%
10%
1%
0.1%
0.01%
0.001%
B W A S B W A S L T U
100%
10%
1%
0.1%
0.01%
0.001%
B: Columbia below damsW: Willamette RiverA: Columbia above damsS: Snake River
L: Lower FraserT: Thompson RiverU: Upper Fraser
Chinook survival in Columbia BasinFall chinook Spring chinook
0.0%
1.0%
2.0%
3.0%
0 200 400 600 800 1000
Upstream (miles)
0.0%
0.5%
1.0%
0 1 2 3 4 5 6 7 8 9
Dams
0.0%
0.5%
1.0%
0 1 2 3 4 5 6 7 8 9
Dams
0.0%
1.0%
2.0%
3.0%
4.0%
0 200 400 600 800 1000
Upstream (miles)
Su
rviv
al
rate
Su
rviv
al
rate
Chinook survival in Fraser Basin
Fall chinookS
urv
iva
l ra
te
0.0%
1.0%
2.0%
0 100 200 300 400 500 600
Upstream (miles)
Myth IVHatcheries are necessary to
mitigate for lost of habitat and over-harvest
The “truth”: hatcheries have strong negative impacts on wild salmon
But: if we eliminate hatcheries we might have no salmon left in some places
Hatcheries
• The basic assumptions– Freshwater habitat is limiting– Egg to smolt survival in the wild is about 5%– Hatcheries can usually obtain 80% egg to smolt
survival– Release smolts ready to go to sea – they don’t
need any freshwater habitat
Why hatcheries were built
• To compensate for over-harvesting
• To compensate for habitat destruction
• To mitigate for dam impacts
• To buffer natural variation
• To provide extra fish for harvest
• To conserve threatened stocks
Total Releases of Chinook - West Coast
0
50
100
150
200
250
300
1873 1893 1913 1933 1953 1973
Release Year
Total Releases of Coho - West Coast
0
20
40
60
80
100
120
140
1873 1893 1913 1933 1953 1973
Release Year
Total Releases of Chum - West Coast
0
100
200
300
400
500
1873 1893 1913 1933 1953 1973
Release Year
Total Releases of Pink Salmon - West Coast
0
200
400
600
800
1000
1873 1893 1913 1933 1953 1973
Release Year
Total Releases of Sockeye - West Coast
0
100
200
300
400
500
1873 1893 1913 1933 1953 1973
Release Year
Total Releases of Steelhead - West Coast
0
10
20
30
40
50
1873 1893 1913 1933 1953 1973
Release Year
Numbers, by ten-year periods, when existing West Coast hatcheries began operations
0
10
20
30
40
50
60
70
80
90
1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990
Ten-Year Periods
Did Hatcheries Work
• We have over 300 hatcheries in the Pacific Northwest
• “If hatcheries were the solution, we wouldn’t have a problem!”
• Much disagreement, what would have happened without hatcheries
OPI Coho Salmon
0
10
20
30
40
50
60
70
1960 1970 1980 1990
Sm
olt
s r
ele
as
ed
0
1
2
3
4
5
Ad
ult
s p
rod
uc
ed
Smolts
Adults
Concerns about hatcheries
• Generate over-harvesting on wild fish in mixed stock fisheries
• Compete with wild fish in freshwater and ocean
• Introduce and exacerbate diseases• Genetically degrade wild fish by
domestication and hybridization• Provide an excuse to allow habitat loss
Pink salmon hatcheries in Prince William Sound
• Largest hatchery program in North America
• 600 million fish stocked each year
• Competing hypotheses re marine fish stocking– stocking augments wild production– stocking replaces wild production
• We have BACI !!!!!!
Area A
year
tota
l ru
n
Guess
Correct
Area B
year
tota
l ru
n
Area C
year
tota
l ru
n
Area D
year
tota
l ru
n
Total return
Area A
Year
Wil
d R
etu
rn
Area B
Year
Wil
d R
etu
rn
Area C
Year
Wil
d R
etu
rn
Area D
Year
Wil
d R
etu
rn
Wild fish production
Prince William Sound
1962 1965 1968 1971 1974 1977 1980 1983 1986 1989 1992 1995
Year
Pin
k s
alm
on
re
turn
Wild
Hatchery
Myth VThe collapse of salmon in the late
80s and 90s is due to habitat changes
The “truth”: habitat has not changed that much
But: habitat is definitely declining
Few (if any) attempts to integrate all factors in combined analysis
• We have detailed harvest models
• We have no hatchery impact models in use
• Changes in ocean conditions are being better understood but not used in evaluating recovery plans
• A number of habitat models, EDT the most used
Framework for impact of habitat
• Multi-stage life history model from Moussalli and Hilborn 1986– each life history stage as a Beverton-Holt curve
with a productivity (initial slope or survival) and a capacity
• Key question is how to relate habitat to productivity and capacity
Sharma coho carrying capacity
0
1200
2400
3600
4800
0 2000 4000 6000 8000 10000 12000 14000
Pool density (m2/km)
Sm
olt
de
ns
ity
Key Model ComponentsSHIRAZ
• Spatially explicit – reaches or estuarine areas
• Life stages as many as you want• Stocks may be life histories, wild/hatchery etc• Capacity and productivity – any life history• Habitat characteristics by reach• Stochastic factors (flows, ocean survival etc)• Functional relationships between habitat
characteristics and stochastic factors and productivity and capacity
Reach Characteristics• Passage• Square meters spawning gravel• Distance• Square meters rearing habitat• Percent fines in gravel• Watershed area by reach• Percent impervious by reach• Temperature, DO etc.
Functional relationships
• Spawning gravel and egg capacity• % fines in gravel and egg to fry survival• Up the the user to define what you want to
use• Will ultimately build a “library” of
functional relationships much like EDT …– But the user will decide which ones to use from
the library
General model framework
• Read in the data – reach-specific habitat– hatchery input– Functional relationships– Hatchery practice– Harvest and ocean conditions specification– habitat interventions
• Loop over time
– Calculate the change in habitat
– Calculate the change in population size
• End the loop
Habitat Changes
• Annual habitat change: habitat degradation
• Habitat change due to a 1-time event: habitat restoration
Hatchery Influence
• Affect wild fish through competition
• Interbreeding can cause domestication of wild fish, and reduced survival
Functional RelationshipsMark I version
• Spawner capacity depends on gravel area
• Egg survival as a function of fines
• Fry survival as a function of percent
impervious and rearing area
Spawners to Egg• capacity depends on gravel area
• productivity depends on age specific fecundity and age distribution of spawners
-
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
8,000,000
0 2000 4000 6000 8000
Spawners
Egg
Eggs to Fry
• capacity is unlimited• productivity depends upon % fines
-
0.050
0.100
0.150
0.200
0.250
0 10 20 30 40
% fines
Egg
su
rviv
al
Fry to Smolt
• capacity determined by rearing area• productivity determined by % impervious
-
0.050
0.100
0.150
0.200
0.250
0 5 10 15 20 25 30 35
% impervious
fry
to s
mo
lt p
rod
uct
ivit
y
Other outstanding issuesBeyond current efforts
• Allow for parameter uncertainty
• Formalize reality checks
• Potentially imbed the above in formal Bayesian framework
Current status
• Muckelshoot tribe using to meet TRT requirements for a rebuilding plan – Green River chinook well developed, White and Lake Washington just beginning
• Joint work with NMFS and Mark Sheuerell to interface SHIRAZ with PRISM dynamic hydrology models
Essential Fish Habitat:SHIRAZ provides a format
• To calculate the sensitivity of population size to each habitat indicator in each area
• This allows a quantitative ranking of the importance of different habitat characteristics and sites
• This ranking can be used to define “essential”, much like NMFS defines “overfishing”
Summary I
• Current work in evaluating natural and anthropogenic impacts on salmon suffer from lack of unified modelling framework
• SHIRAZ can serve as an initial general model structure for cost benefit analysis, policy evaluation, and parameter estimation