Comparative Feeding Ecology of Coastal Cutthroat Trout and

Rainbow Trout in the Cedar River, Washington with an emphasis on

Consumption of Juvenile Salmonids

Roger Tabor, Hans Berge, Dan Lantz, Matt Klungle, and Brad Thompson

Acknowledgements

Chad Jackson

Brant Boelts

Nathanael Overman

Steve Foley

Kelly Kiyohara

Clayton Kinsel

Scott Scheutzler

Will Morris

Nate Martens

Yong-Woo Lee

Todd Kassler

Craig Busack

Anne Bagley

Bruce Bolding

Shannon Vincent

Devin West

Lindsy Wright

Ben Price

James Curtis

Tracy Leavy

Jeff Chan

Scott Sanders

Terence Lee

Dan Spencer

Steve Damm

Keith Sweeney

Howard Gearns

Tim Romanski

Nathan Hyde

Eric Tallman

WDFWUSFWS

SPU

Gary Spraque

Paul Faulds

Cedar River AFC

Kollin Higgins

Jim Lissa

Eleanor Bosman-Clark

Ray Timm

Frank Leonetti

King County

Trout Unlimited

Private LandownersTim Allen

Julie Stachawiak

NOAA Fisheries

Sean Naman

Peter Kiffney

Thomas Buehrens

Chester

Morse Lake

Lake Washington Basin

Cedar Falls

Seattle

Cedar River

Landsburg

Diversion Dam

Puget

Sound

Lower

Middle Upper

1995 - Closed to fishing

2003 – Trout abundance estimate~17,500 trout > 200 mm (8”)

2004 - Catch and Release fishery opened

2005 - WDFW tasked to predict the impacts of alternate fishery regulations

2006-2010 - WDFW, King County, and USFWS study to estimate abundance, size distribution, and feeding habits of trout

Background

Methods - Electrofishing Techniques

Summer

Tote-Barge electrofishing

Winter-Spring

Raft electrofishing

Also angling used Also backpack electrofishing used

Diet and Predation Estimation

• Gastric lavage

• Identify stomach contents

• including DNA analysis

• Predation estimation

• Direct consumption model

• Population estimate used to estimate total consumption

• Mark-resight method – summer

• Snorkel counts - winter

Methods - Four Strata

S-2

S-3S-4

S-1

• Strata based on gradient, natural confinement, and channel type

Strata

Species composition Lower Cedar River

0

20

40

60

80

1 2 3 4

Pe

rce

nt

Cutthroat trout, n = 670

Rainbow trout, n = 1,307

Species composition

Lower Cedar

0

20

40

60

80

100

LakeWashington

1 2 3 4 MiddleCedar

Pe

rce

nt

Cutthroat trout

Rainbow trout

2015 -2016

Clark and Beauchamp, UW Kiffney, NOAA Fisheries2006-2010

0

20

40

60

80

100

Lake Washington Lower Cedar Middle Cedar

Pe

rce

nt

Lake and

Mainstem

Small

Tributaries2009-2013

Urbanized Undeveloped

Cutthroat trout

• small streams

• low gradient streams

• proximity to lakes

Rainbow trout

• large streams and

rivers

• medium to high

gradient streams

Hartman and Gill 196866 southwestern British Columbia streams

Summer Diet and PredationOne two-week period (July-August) in 2006 and 2007

Summer Diet2006 and 2007 combined, percent by weight

Cutthroat Trout Rainbow Trout

Winter-Spring Diet and Predation

Cutthroat trout - 2010Diet, percent by weight, all strata combined

0

20

40

60

80

100

Pe

rce

nt

Size class (mm)

Other

Terr. invert.

Aq. insects

Crayfish

Fish eggs

Other fish

Sculpin

Coho

Chinook

Sockeye

18 2622 23 27 21 26 77 34

Jan-Feb Mar-Apr May-Jun

Rainbow trout - 2010Diet, percent by weight, all strata combined

0

20

40

60

80

100

Pe

rce

nt

Size class (mm)

Other

Terr. invert.

Aq. insects

Crayfish

Fish eggs

Other fish

Sculpin

Coho

Chinook

Sockeye

25 7738 28 40 61 16 46 52

Jan-Feb Mar-Apr May-Jun

0

5

10

15

20

25

30

35

Summer Win-Spr Summer Win-Spr

Cutthroat trout Rainbow trout

Perc

en

t p

isciv

oro

us

< 200 mm

> 200 mm

196 147

130

81

197

299

281

193

Percent Piscivorous

0

20

40

60

80

100

120

0 100 200 300 400 500

Fork length (mm)

0

20

40

60

80

100

120

140

other

sculpin

coho

Chinook

sockeye

Prey length

Pre

y le

ng

th (

mm

)

Cutthroat trout

Rainbow trout

0

50

100

150

200

250

300

< 150 150-249 >250

Size class (mm)

0

50

100

150

200

250

300

< 150 150-249 >250

Size class (mm)

2008

2010

Cutthroat trout

Rainbow trout

Maxim

um

num

ber

of

sockeye

Maximum number of Sockeye fry

Food Specialization by Individual Trout (Bryan and Larkin 1972)

Four Rainbow Trout stomach samples

Summary• Within the Lake Washington Basin, cutthroat trout

are the dominant trout species in the lake, lower end of the Cedar River, and in small streams

Summary

• Predation of sockeye was most evident in small cutthroat trout and large rainbow trout

• Consumption of sockeye was highest in large rainbow trout

• Predation of juvenile Chinook was observed primarily in cutthroat trout

• Cutthroat trout are piscivorous at a smaller size than rainbow trout

• As cutthroat trout grew they shifted to larger prey including sculpins and crayfish

• Relative consumption of salmonid prey may reflect differences in habitat use by both predator and prey

Summary

Questions

roger_tabor@fws.gov