Emigration behavior of resident and anadromous juvenile O. mykiss:

exploring the interaction among genetics, physiology and habitat

Sean Hayes, Chad Hanson, Morgan Bond, Devon Pearse, Andrew Jones, Carlos Garza, Bruce MacFarlane

•Small watershed (75km2)

•23km of stream accessible to anadromous fish

•“native” resident fish above barriers

•Small hatchery

•Dynamic flow regime(28m3 s-1 to 0.1m3 s-1)

•Small Estuary (closes seasonally)

Scott Creek

Map: Rob Schick, NMFS

Scott Creek O. mykiss life history strategies

Ocean

upper watershed estuary/lagoon

Upstream resident

Mature in estuary(never enter ocean)

xx

x

3 km

Adultweir

InstreamPIT tagreaders

Scott Creek

X= barrier

Seine, hook & line, and electrofishing

Smolttrap

Resident populations“diverged” >100 yrs ago

Big Creek Adults

Weir Adults

Lagoon Juveniles

60

Hatchery Juveniles

Scott Creek Adults

76

Mill Above

Big Creek, Boyer

63

92

Big Creek Above

68

Scott Creek Above

Neighbor-Joining distance tree, with bootstrap values for supported nodes

Do rainbow trout and steelhead differ?

xx

x?

Proportion of fish assigned to Resident or Anadromous ancestry by habitat

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Above Barrier

Upstream Smolt trap Estuary

Anadromous

Resident

Genotype distribution in upper watershed

0.00

0.10

0.20

0.30

0.40

50 70 90 110

130

150

170

190

210

230

250

270

Fork length

Fre

qu

ency

Resident (n=128)Anadromous (n=209)

Emigration rate from above

anadromy barrier

• 400 fish PIT tagged above

• 2.3 % over the falls

• 1.8 % detected at smolt trap

Na+ K+-ATPase Physiology

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

AT

Pas

e ac

tivity

0

2

4

6

8

Smolt TrapEstuary

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

AT

Pas

e ac

tivity

0

2

4

6

8

Above Barrier Upstream

?

Upstream samples

0.00

2.00

4.00

6.00

8.00

0 2 4 6 8 10 12Month

AT

Pa

se

ResidentAnadromous

Na+ K+-ATPase Physiology

0

2

4

6

0 2 4 6 8 10 12 14 16ATPase

Fre

qu

ency

ResidentAnadromous

Why do wild fish migrate at such small sizes?

0

0.04

0.08

0.12

0.16

50 70 90 110

130

150

170

190

210

230

250

Fork Length (mm)

Fre

qu

ency

Typical steelhead smolt size distribution

Lagoon- Sand Bar Closed (July-Dec.)

Estuary- Open to Ocean (Jan.-June)

Does estuary serve as nursery habitat?(Morgan Bond’s thesis)

Black lines indicate upper watershed growth

Blue lines indicate migration to estuary and growth

Jan Jul Jan Jul Jan Jul Jan Jul Jan

For

k Le

ngth

(m

m)

0

50

100

150

200

250

Mean

5th %

95th %

YOY 1+ 2+ 3+

Is the estuary a nursery?

Ocean

upper watershed estuary/lagoon

85% of returningadults use estuary pathway

Size threshold for ocean survival

What happens when water quality degrades?

3 km

>45% detected moving Upstream each fall(probably >90%)

Size of recaps at smolt trap in spring

0

2

4

6

8

10

12

14

16

18

20

60 80 100 120 140 160 180 200 220 240 260 280 300Fork Length

Fre

qu

en

cy

Upstream

Estuary (previous summer)

X

A tale of two watersheds

Functional estuary present

No estuary available

Year 1 Year 2 Year 3

Year 1 Year 2 Year 3

(in Central California…)

AcknowledgementsFunding• NMFS • DFG FRGP• NURP• California Sea Grant

Land Owner support•Big Creek Lumber Company•The Wilson Family•Monterey Bay Salmon and Trout Project•Cal Poly Swanton Ranch•Lockheed Martin

Implications of resident trout studies

• Should residents be counted in steelhead populations for delisting criteria?

• Residents may become steelhead, but this probably happens at low frequencies

• Results of resident contribution to anadromous breeding pending

Estuary Environmental Conditions

“Lethal”levels

Influence of genotype on migration behaviorTo sea or not to sea?

Genotype Frequencies

0

0.2

0.4

0.6

0.8

1

Upstream Smolt trap

Fre

qu

en

cy

Resident

Anadromous

Typical spring downstream migrant (smolt?)

After 5-6 months rearing in estuary

100mm

Steelhead in Scott Creek

85% of returningadults use estuary pathway

Fork Length (mm) at Trap

Big smolts are less likely to stayP

roba

b ili t

y o f

rec

aptu

re

< <150 >1500

5

10

15

20

25

ConclusionsCentral Coast steelhead adapt for estuarine use

Steelhead strategies without estuary• Longer upstream rearing• Fewer smolts, reduced anadromy?

Figure 5. Estimated lagoon yearly population sizes and yearly mean growth rates from 2003-2006 (left y-axis). The bar graph (right side y-axis) represents mean fork length of fish sampled in the estuary in late fall of each year, just prior to winter storm season and lagoon opening. Years match points within labeled column. All data are means ± SE, R2=0.99. Regression P= 0.005

Estimated Lagoon Population

0 500 1000 1500 2000 2500 3000

SG

R l

eng

th a

s a

% p

er d

ay

0.2

0.4

0.6

0.8

1.0

2005 2004

20032006

Density-dependent Estuary Growth in Steelhead

Implications for Local Rivers

• Larger river- may have more rearing capacity= larger smolts upstream

• BUT… is there enough water?

• Estuary issues– Breaching– Estuary size reduced?– Enough flow to connect with watershed?

Lagoon fish move upstream in the fall and then back down in spring

Lagoon fish PIT tag reader detections

0

50

100

150

200

250

300

350

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Fre

qu

en

cy

Upper watershed

Lower watershed

>45% lagoon fish detected moving upstream

Escapement

Early 20th century spawning population was 4-10 times larger

Why is estuary growth so good?(Jeff Harding’s diet studies)

Lots of food!Diet consists of Corophium and Eogammarus sp.

But where does food come from?

• Upper watershed growth poor

• Insect diet

• Low flow

• Low light– low nutrient input into estuary

Hypothesis- Nutrient flow from marine derived nutrients (kelp) enhances productivity (Alison Collins senior thesis)

Terrestrial Marine

Mar

ine 13C and 15N from Juvenile Steelhead

13 C (0/00) +/- SD

-26 -24 -22 -20 -18 -16 -14

15 N

(0/

00)

+/-

SD

6

8

10

12

14

16

Juv. Steelhead - Lagoon

Juv. Steelhead - Above Fall

Adult Steelhead

Coastal Marine Fish

Why don’t all fish recruit to the estuary?