What is Variability ?

Change with location or through time in the capacity of a freshwater system to support salmon

• Spatial Variation– Natural variability in conditions

– Variable intensity of human impacts

– Interaction between watershed condition and human effects

• Temporal Variation– Interannual variation in weather

– Catastrophic disturbance

– Cyclical or unidirectional changes in climate

• Spatial-Temporal segregation is artificial - temporal changes in condition are a major factor in creating spatial variation

Variability in Annual Coho Production

Bisson and Bilby 1998

0

1

2

3

4

5

6

7

2 4 6 8 10 12 14 16 18 20 22

Num

ber o

f Stu

dies

Juvenile Coho Production (g/m2/y)

Snohomish Index Sites

02

468

101214

1618

Foye

Patte

rson

Unna

med

6

Unna

med

15

Unna

med

7 Ross

Alle

n

Deep

Unna

med

10 Lake

Pant

her

Unna

med

9

Cath

erin

e

Lang

lois

Unna

med

16

Unna

med

8

Unna

med

17

Unna

med

4

Qui

lced

a

Dubu

que

Cany

on

Bosw

orth

Unna

med

2 Boyd

Unna

med

11 De

er

Wor

thy

Unna

med

5

Peop

les

Brid

al V

eil

Unna

med

3

Unna

med

19

Unna

med

13

Trib

to B

oyd

Grif

fin

Harr

is

Unna

med

12

EF G

riffin

Lew

is

Unna

med

18

Unna

med

14

% o

f Tot

al F

ish

(198

4-19

98)

R

eg

ressio

n C

oe

ffic

ien

t

1984 1988 1992 1996 2000

-1.0

0.0

1.0

Urban

1984 1988 1992 1996 2000

-0.1

50

.00

.10

Rural

1984 1988 1992 1996 2000

-2-1

01

2

Agriculture

1984 1988 1992 1996 2000

-0.0

60

.00

.04

Forest

1984 1988 1992 1996 2000

-1.0

0.0

1.0

Re

gre

ssio

n C

oe

ffic

ien

t

Road

1984 1988 1992 1996 2000

-2-1

01

2Wetlands

1984 1988 1992 1996 2000

-1.0

0.0

1.0

Water

1984 1988 1992 1996 2000

-0.2

0.2

Unstable

1984 1988 1992 1996 2000

-20

12

Re

gre

ssio

n C

oe

ffic

ien

t

Advanced Outwash

1984 1988 1992 1996 2000

-0.1

0.1

Recessional Outwash

1984 1988 1992 1996 2000-0

.06

0.0

0.0

4

Till

1984 1988 1992 1996 2000

-20

12

Peat

1984 1988 1992 1996 2000

-0.4

0.0

0.4

Re

gre

ssio

n C

oe

ffic

ien

t

Alluvium

1984 1988 1992 1996 2000

-0.1

00

.00

.10

Bedrock

1984 1988 1992 1996 2000

-0.3

0.0

0.2

Drainage Area

Factors Associated with Coho Salmon AbundanceSnohomish Basin

Pess et al. 2002

Temporal Variation

• Year-to-year variation in flow, temperature etc.• Life history specific effects

• Examples • Winter floods - decreased egg-fry survival

• Spring high flows - increase fry emigration

• Summer drought - decreased summer fry survival and growth

• Autumn high flow - enhanced access to spawning habitat

• Long-term variations• Recovery from disturbance

• Climatic changes (PDO, global warming)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

0 1 2 3 4 5 6 7 8Flow Return Interval (yrs.)

Rec

ruit

s/S

paw

ner

Winter Flow and Population Performance

Unpublished data, Beamer and Pess (with apologies)

Pro

duct

ivity

0 10 100 500

A

B

C

D

E

F

low

high

Time Since Disturbance (yrs)

Temporal Changes in Salmonid Production

Temporal Changes in Salmonid Diversity D

iver

sity

0 10 100 500

low

high

Time Since Disturbance (yrs)

A

G

H I

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

81 82 83 84 85 86 87 88 89 90 91

Hoffstadt Cr.

Herrington Cr.

Schultz Cr.

Juve

nile

Coh

o P

rodu

ctio

n (m

g/m

2 /d)

Bisson et al. 1997

Coho Salmon Productivity after the Eruption of Mt. St. Helens

Year

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

86 87 88 89 90 91 92

Year

sculpin

dace

salmonid

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

86 87 88 89 90 91 92

Year

sculpin

dace

salmonid

Disturbed Site

Buffered Site

Den

sity

(fi

sh/m

2 )D

ensi

ty (

fish

/m2 )

coho

0+ steelhead

1+ steelhead

0+ cutthroat

1+ cutthroat

2+ cutthroat

5 Years after Disturbance 60 Years after Disturbance

Thrash CreekBiomass = 3.00 g/m2

Beaver CreekBiomass = 3.28 g/m2

Hicks et al. 1991

Year 0 Year 50

Patterns in Stream Productivity

Low

Medium

High

Questions

1) How can variability be incorporated into predictions of salmon capacity, growth and productivity?

2) What are the largest sources of uncertainty in predicting salmon response to freshwater habitat conditions?

3) What alternative scenarios of current and future conditions should the model strive to explore?

4) At what spatial scale should wood abundance be characterized to be most meaningful to salmon?

5) What habitat is most important; freshwater, estuarine or marine?

6) What nutrient contribution from salmon carcasses is required to achieve maximum smolt production? How can this aspect of habitat be incorporated into the model?

Q 1&2: Incorporating Variability

• Spatially explicit predictions - recognize that not all places are equal and a few locations can support the majority of all freshwater production

• Most influential life history stage varies interannually; build in hydrological fluctuations (flood, drought) and adjust the survival of the affected life history stage accordingly

• Major disturbance events cause predictable patterns of change in productivity

• Recognize that the performance of the fish at one stage influences survival later in life; higher spring-summer growth rates increase overwinter survival; larger smolt size increases marine survival

• Failure to include factors other than physical habitat in relationships to salmon production a major source of uncertainty in current modeling approaches

What is Salmon Habitat?

Combination of physical, chemical and biological attributes

• Physical– Access

– Sediment levels, channel morphology

• Chemical– Water temperature

– Contaminants

– Nutrient availability

• Biological – Primary and secondary production

– Competition and predation

.

Q 3: Habitat Scenarios

• High Quality Salmon Habitat– Low Elevation

– Low Gradient Channels

– Diversity of Riparian and Channel Conditions

– Low-level of Human Influence

People and Salmon Occupy Similar Habitats

Urbanization Effects on Fish Communities

0

20

40

60

80

100

0 20 40 60

Urbanization (% Impervious Area)

% C

oho

% of fish community composed of coho salmon with increasing levels of urbanization for 11 watersheds in King County, Washington. From Lucchetti and Furstenberg 1993.

Population in King, Pierce and Snohomish Counties

0

400

800

1200

1600

2000

1880 1900 1920 1940 1960 1980 2000

Year

Pop

ulat

ion

(x10

00)

Alternative Growth Scenarios

• Future development will disproportionately impact sites with high productive potential

• Evaluate effect of different patterns of development– Concentrate new growth in already populated areas

– Unrestricted development focused on low relief, low elevation locations

– Current zoning plans

Q 4: Appropriate Scale for Wood

• Wood-fish relationships are tenuous

• Relates to failure to consider other aspects of habitat

• Best relationships with winter abundance of coho salmon

• Ideally, wood abundance and distribution at the watershed scale

• Response to wood in a reach with a mix of conditions typically associated with high production will be greater than in a reach with poorer underlying condition for the fish

Q 5: Which Habitat is Most Important

•Answer - All•Relative importance vary with conditions

–Poor freshwater habitat and extreme weather conditions sufficient mortality may occur prior to smolting to preclude adjustments later–More benign freshwater conditions and enough smolts may be produced to exceed estuarine capacity–Recent experience on the Columbia indicates the significance of early marine rearing condition

•All habitats are connected•Freshwater conditions can influence smolt size and number - affects survival in the estuary and ocean•Estuarine conditions can also effect size and number of fish entering the ocean•Ocean conditions dictate adult growth and survival, influences the number of fish returning and delivering nutrients to freshwater - influences freshwater habitat condition

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Oct. Nov. Dec.

Carcasses

No Carcasses

Ave

rage

Wei

ght (

g)

salmon carcasses present

Bilby et al. 1998

Q 6: Nutrient Contribution from Spawning Salmon

Snoqualmie

Deschutes

Chehalis

Hoh

Hoko

Willapa

Skagit

BogachielSoleduck

Dickey

Skykomish

Clallam

Sample Locations

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.2 0.4 0.6 0.8

Inde

x of

15N

Enr

ichm

ent

Carcass Availability (kg/m2)

Bilby et al. 2001

0

30

60

90

120

150

Watershed

Car

cass

De

nsi

ty (

fish

/km

)

Approximate 15N Saturation Level

Bilby et al. 2001