The importance of location: Responsiveness of

stream-living fish populations

Brooke PenalunaUSFS PNW Research Station

Oregon State University

Co-authors: S. Railsback, J. Dunham, S. Johnson, A. Skaugset, and R. Bilby

Trask Watershed Fish component: multiple lines of inquiry

Location within landscape matters

Stream flowStream temperatureTurbidityNutrients

Stream gradientStream shapeHabitat unitsVelocity shelterHiding coverSpawn gravel

Habitat template

Environmental regimes

Headwater streams are ideal to study location-related processes

Headwater streams can be quite different

Pothole

RockUpper Mainstem (UM)

Gus

Trask River Watershed

Trout demography is unique to each siteGUS

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POT

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ROCK

80-8384-8788-9192-9596-99 100-103

104-107108-111112-115116-119120-123124-127128-131132-135136-139140-143144-147148-151152-155156-159160-163164-167168-171172-175176-179180-183184-187188-191192-195196-199200-203204-207

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length class (FL; mm)

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1) What is the spatial variability of fish population biomass across

headwater streams?

2) What is the role of environmental regimes and the habitat template to

fish population biomass? Habitat template Environmental regimes

Using an Individual-based Model to understand complex interactions

1) Individuals grow and change2) Variability among individuals of same age3) Resources used by individuals reflect availability 4) Population abundance is based on field data

Goal: to compare fish biomass to observed patterns from fieldGrimm and Railsback 2005

Spatial Temporal

tx

y z

individuals

population

community

inSTREAM model

individual behavior

population responses

Environmental RegimesStream temperature, flow, and turbidity

Habitat templateChannel shape, velocity shelter, hiding refuge, and spawn gravel

1) What is the spatial variability in fish population biomass across

headwater streams?

Headwater streams from same watershed can have very different

population biomass densitiesbiomass

biomass of trout (g)

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2000

4000

6000

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12000GusPotholeRockUM

2007 2008 2009 2010

Headwater streams have significantlydistinct fish responses

Gus Pothole Rock UM

Biomass data using 5 age classesTransform: square rootResemblance: Euclidean distance

4 years x 2 seasons = 8 points per siteAll pairwise comparisons significant P<0.05

Higher biomass

Lower biomass

Fish populations differ even within a few hundred meters within the same watershed

But, what are these differences due to? Fixed habitat template or dynamic environmental regimes?

GusRockPotholeUpper Mainstem

GusRockPotholeUpper Mainstem

2) What is the role of environmental regimes and the habitat template to

fish population biomass? Habitat template Environmental regimes

Even with differing environmental regimes fish populations maintain

similar responses

biomass

biomass of trout (g)

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18000GusPotholeRockUM

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biomass

biomass of trout (g)

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4000

6000

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2007 2008 2009 2010

Habitat template controls fish response

Gus Pothole Rock UM

Higher biomass

Lower biomass

4 years x 2 seasons x 4 sites = 32 points per siteAll pairwise comparisons significant P<0.05

Next step: examine alternative scenarios

Stream flowStream temperatureTurbidityNutrients

Stream gradientStream shapeHabitat unitsVelocity shelterHiding coverSpawn gravel

Habitat template

Environmental regimes

Forest harvest Climate change

Conclusions• Fish populations among headwater streams respond

differently to same factors because the habitat template controls fish responses

• Headwater streams with higher heterogeneity in their habitat template also had higher fish biomass

• This may suggest that certain headwater streams may be more sensitive than others to changes in environmental regimes from climate change or forest harvest

AcknowledgementsFunding sources: EPA STAR grant, USGS FRESC, Trask

Watershed Study www.watershedsresearch.org, OSU graduate school and FW departmental scholarships, AFS scholarships, USFS PNW

PhD committee: Jason Dunham, Steve Railsback, Sherri Johnson, Lisa Ganio, Matt Betts, Jim Hall

Field help: Boyd Carroll, Ben RamirezGraphics help: Kathryn Ronnenberg, Ivan Arismendi