Role of Tidal Saltwater Habitats for Juvenile Salmonids

(Myths vs Reality in the Columbia River Estuary)

Ed CasillasNWFSC, Seattle, WA

(Contributors – UW, OSU, OHSU, WDFW, PSU, COE, BPA)

Current Drivers - Population viability & resilience, habitats salmon use and need• Productive feeding area

• Refuge from predators

Role of EstuariesHistorical Drivers – Production, abundance, mortality• Conduit – Connect upstream spawning and rearing areas to

ocean habitat

• Transition to saltwater

2002 2003 2004

J M M J S N J M M J S N J M M J S N J M M J S N

Log

10 C

PU

E

0.0

0.5

1.0

1.5

2.0

2.5

3.0

2005

Marine

Mixing

Tidal fresh

Marine

Mixing

Tidal Fresh

Myth - Juvenile salmon use the estuary for a short period of time (as individuals and as populations)

Reality – Juvenile salmon present in the estuary year around

Myth – Salmon populations predominantly use the subyearling and yearling strategy to succeed

Reality - All ESUs use a variety of juvenile life history strategies to succeed

Alevins

Fry 40-60mmFingerlings 60-90mm

Subyearlings/Yearlings100-200 mm

Size seen in the ocean, composed of juveniles using fry, fingerling, subyearling, and yearling strategy

Fry – distributes throughout the river, estuary and oceanFingerlings – rears near spawning area for 1-2 months, then distributes throughout river, estuary, and oceanSubyearling/Yearling – rears in river, then migrates to the ocean

>50% of juvenile enter estuary at < 60mm

Month

Mea

n Pe

rcen

t

Monthly Fry Proportion

Fry a Dominant Strategy in the Columbia River Estuary

Fry

Month

J F M A M J J A S O N D

Size

(m

m)

30

35

40

45

50

55

60

Lower estuary

Mixing zone

Tidal freshwater

WC-F WC-SpSCG-FUCR-Su/FWR-SpSnake-FRogue

Fry Strategy Used by Many Chinook ESUs in the Columbia River

Myth - Juveniles only use the estuary to transit to the ocean

Reality – Juveniles grow in the estuary

0 30 60 90 120 150 180 210 240 270 300 330 360

Mea

n F

L (

se)

20

40

60

80

100

120

140

160Lower EstuaryMiddle estuaryTidal Freshwater

Day of yearJ F M A M J J A S O N D

Corollary – If juveniles grow in the estuary, they then must reside in the estuary

• Juveniles enter the estuary over a wide range of sizes

• Residence time decreases with size at estuary entry

Data from Lance Campbell

Point Adams Beach 2004

May-Aug

y = -0.9705x + 110.91

R2

= 0.5172

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120

Back Calculated Fork Length at Estuary Entry (mm)

Res

iden

cy (

day

s)

Estuary habitat use and residency is size related

• Small size classes frequent shallow, nearshore and wetland habitats

• Few juveniles > 90 mm enter or remain in interior marsh channels

Chinook Length Frequency in Wetland ChannelsWhich Habitats are Used

by Juvenile Salmon April

0

10

20

30

40

50

60

35 40 45 50 55 60 65 70 75 80 85 90 95 100

Fork Length (mm)

Fre

qu

en

cy

May

0

5

10

15

20

25

30

35 40 45 50 55 60 65 70 75 80 85 90 95 100

Fork Length (mm)

Fre

qu

en

cy

June

0

2

4

6

8

10

12

14

16

35 40 45 50 55 60 65 70 75 80 85 90 95 100

Fork Length (mm)

Fre

qu

en

cy

July

0

1

2

3

4

5

6

7

35 40 45 50 55 60 65 70 75 80 85 90 95 100

Fork Length (mm)

Fre

qu

en

cy

April

May

June

July

n = 155

n = 122

n = 39

n = 19

2004

Freq

uenc

y of

Occ

urre

nce

Fork Length (mm)

Scrub-Shrub

Forested

Emergent

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

CS WSI PAB PE UCC ETI LES

% I

RI

Diptera (adult) A. salmonis A. spinicorne Cladocera Other prey items

tidal freshwatermarine estuarine mixing

Myth – Juvenile salmon feed primarily on benthic aquatic organisms

Reality – Juvenile salmon feed dominantly on terrestrially derived insects

40-80mm70-120mm 60-90mm

Myth – The Columbia River Estuary Benefits Lower River stocks only

Reality - Most all ESUs use estuarine habitats -Stock composition varies through the year

0%

10%

20%

30%

40%

50%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovFrom David Teel

Stock Composition Chinook Salmon 2002 - 2006

All Beach Seine Sites Combined

Minor contributors Only

0%

20%

40%

60%

80%

100%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

UCR Su / F

W Cascade F

W Cascade Sp

Spring Cr F

Willamette Sp

Snake F

Deschutes F

Rogue F0%

10%

20%

30%

40%

50%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0%

10%

20%

30%

40%

50%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovFrom David Teel

Stock Composition Chinook Salmon 2002 - 2006

All Beach Seine Sites Combined

Minor contributors Only

0%

20%

40%

60%

80%

100%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

UCR Su / F

W Cascade F

W Cascade Sp

Spring Cr F

Willamette Sp

Snake F

Deschutes F

Rogue F

CREST

Myth – Only subyearling from lower river stocks use wetland habitats

Reality – Subyearlings and yearlings from interior basin also use wetland shallow water habitats

Pit tag detector array in secondary wetland channel

2009 DetectionsLower Columbia River Chinook salmon, N=32

Lower Columbia River coho salmon, N=5Snake River fall Chinook salmon, N=1

Snake River spring Chinook salmon, N=1Snake River summer steelhead, N=3

From Burke, 2005. Data from Rich (1920) & Dawley et al. (1985)

If estuaries provide opportunity for diversification of life history strategies and diversity is an attribute of healthy salmon populations, how does the Columbia River system fare?

Estimated changes in the relative proportions of juvenile salmon life histories

Jan Mar May Jul Sep Nov Jan Mar May Jul

Rel

ativ

e A

bu

nd

ance

Fry with platelets only

Fry (<60 mm)

Fingerling - Recent Arrivals

Fingerling - Fluvial rearing

Fingerling - Estuarine Rearing

Fingerling - Fluvial and additional rearing

Yearling

Historic

Jan Mar May Jul Sep Nov Jan Mar May Jul

Jan Mar May Jul Sep Nov Jan Mar May Jul

Rela

tive

Abu

ndan

ce

Fry

Fingerling Natal / Fluvial Rearing

Yearling

Contemporary

Simplication of life histories may undermine resilience and recovery of Columbia River Chinook salmon

Can Salmon Life History Diversity be Restored?

Estuarine restoration, life history strategies, and adult returns; the Salmon River story

1975

0

20

40

60

80

100

1976

CPU

E (n

umbe

r/se

ine

haul

)

0

20

40

60

80

100

1977

Mar May Jul Sep Nov

0

20

40

60

80

100

Lower estuaryMid estuary

Upper estuary 75' seine (1977)Upper estuary 125' seine (1977)

2000

0

20

40

60

80

100

2002

Mar May Jul Sep Nov

0

20

40

60

80

100

2001

CPU

E (n

umbe

r/se

ine

haul

)

0

20

40

60

80

100

Lower estuaryMid estuaryUpper estuary

• Life history diversity has expanded with increased wetland opportunity

Can Life History Diversity be Restored? After Estuary RestorationBefore Estuary Restoration

Size at Estuary Entry for Juveniles at Mouth (BY 2001 & 02)

Emergent Fry < 45mm 7%Spring (MAM) 47 – 64 mm 10%Summer (JJA) 55 – 96 mm 77%Fall (SON) 97 – 109 mm 6%

Myth – Estuarine restoration does not affect adult returns

Reality – Recovered life history strategies contribute to adult returns

Size at Estuary Entry for Adults (2004 RY; n=145)

Emergent Fry < 45 mmSpring (MAM) 47-64 mmSummer (JJA) 65-96 mmFall (SON) 97-110 mm

17%14%57%12%

Summary – Estuary as Salmon Habitat

• Based on distribution preferences and growth characteristics, estuary a habitat for smaller juvenile salmon to grow

• Shallow water, low velocity, and low salinity surface environments with associated wetland vegetation are features that define habitat

• Diverse distribution of habitat a surrogate for diversity and spatial structure of salmon population

• All juveniles benefit from estuary habitat through food webs and predator refuge

• Preservation and restoration of shallow water, low velocity, and low salinity environments an important strategy for recovery of salmon and to mitigate for anthropogenic modifications