Growth Trajectories of Wild California Steelhead Parr

David Swank1,2, Will Satterthwaite1, Michael Beakes1, Susan Sogard2, Marc Mangel1, Rob Titus3, Joe Merz4

1UC-Santa Cruz; 2National Marine Fisheries Service; 3California Dept of Fish and Game; 4East Bay Municipal Utilities District

Previous work (Thorpe et. al. 1998) on the life-history of Atlantic salmon has shown that:

• In juvenile development, maturation in the stream as a resident parr and smolting are mutually exclusive.

• The fastest-growing juveniles in a cohort mature as resident parr, the next fastest become smolts, while the slowest remain immature parr in stream for another year.

• A decision window occurs in the fall preceding smolting, during which the juvenile salmon decides which pathway to follow.

Hypothesis

•O. mykiss follow life-history decision rules similar to Atlantic salmon.

•Stream temperatures, stream flows, and food availability differ between coastal California and Central Valley streams, and will affect juvenile growth.

•The resulting differences in juvenile growth rates should result in significant differences in life-histories among these populations.

Objectives

•Characterize growth rates and life-history pathways of juvenile steelhead in two coastal California populations and two Central Valley populations.

•Incorporate these data as part of a model that predicts how changes in flows on managed rivers can affect growth rates and therefore life-histories of wild steelhead populations.

Scotts Creek Soquel

Creek

American R.

Mokelumne R.

Legend

Soquel Creek Watershed¸0 4 82

Kilometers

Scotts Creek

Soquel Creek

Coastal Estuaries = Critical Nursery Habitat

Lower American River

Lower Mokelumne River

Monthly Mean Water Temperature2006-2007

4

6

8

10

12

14

16

18

20

May July September November January March May

Deg

rees

(C

)Soquel Creek American RiverScotts Creek Mokelumne River

Methods

•Juvenile steelhead were sampled by seasonal (June, Oct., Dec.) electrofishing at four sites on Scotts Creek from 2006-2007 and four sites on Soquel Creek from 2003-2007.

– Additional samples came from a smolt trap on Scotts Creek, and seining in Scotts Creek Lagoon.

•Juvenile steelhead were sampled by seine and hook and line at three sites on the American River, and two sites on the Mokelumne River.

– Additional data came from boom electrofishing by EBMUD on the Mokelumne River.

Methods

• Elastomer tags were placed on all steelhead < 65 mm fork length (FL) in the spring, and PIT tags on all steelhead > 64mm FL.

• Length, weight, and scale sample• Gastric lavage on a subsample of fish

• Invertebrate drift samples (monthly)• Benthic samples (quarterly)

Drift densities are higher in Central Valley streams

REGION

Me

an

+/-

95

% C

I Dri

ft D

en

sity

Central Valley Coast-200

200

600

1000

1400

1800

2200

Growth Rate (mm/day) from PIT tag recaps

0

0.2

0.4

0.6

0.8

1

1.2

Mokelumne American Scotts Soquel

Gro

wth

Ra

te (

mm

/da

y)

YOY Steelhead Growth - by Stream

0

50

100

150

200

250

300

3-Mar 22-Apr 11-Jun 31-Jul 19-Sep 8-Nov 28-Dec

Me

an

Fo

rk L

en

gth

(m

m) American R.

Mokelumne R.

Soquel Crk.

Scotts Crk

Average length over a year for steelhead parr in the four studystreams based on PIT tag recaptures; all periods and sites combined.

Aug 2nd 2006, Sunrise (American River)

126mm FL and 60mm FL

Growth among sites

All Periods combined 2006-2007

0

0.05

0.1

0.15

0.2

0.25

Swanton Upper Scotts Big Creek Lower Scotts

Site

Gro

wth

Rat

e (m

m/d

ay)

All Periods combined 2006-2007

0

0.05

0.1

0.15

0.2

0.25

Ashbury BadgerSprings

GS Falls Lion's Park

Site

Gro

wth

Rat

e (m

m/d

ay)

Scotts Creek Soquel Creek

Growth rates (mm/day), by site and time period for PIT tagged juvenile steelhead in Scotts Creek, 2006-2007. Error bars are +/- 2 standard errors.

0

0.05

0.1

0.15

0.2

0.25

0.3

June-Sept June-Dec Sept-Dec Dec-June 1 Year+

Period

Gro

wth

Rat

e (m

m/d

ay)

Swanton Upper Scotts Big Creek Lower Scotts

Growth among time periods – Scotts Creek

Growth rates (mm/day), by site and time period for PIT tagged juvenile steelhead in Soquel Creek, 2006-2007. Error bars are +/- 2 standard errors.

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

June-Sept June-Dec Sept-Dec Dec-June 1 Year+

Period

Gro

wth

Rat

e (m

m/d

ay)

Ashbury Badger Springs GS Falls Lion's Park

Growth among time periods – Soquel Creek

Scotts Creek Smolt Trap Recaptures

50

70

90

110

130

150

170

190

May-06 Jul-06 Aug-06 Oct-06 Nov-06 Jan-07 Mar-07 Apr-07 Jun-07

Capture Date

Fo

rk L

eng

th (

mm

)

Length at capture of juvenile steelhead caught in the Scotts Creek smolt trap. Each point represents a single capture event. Only the last capture for each fish was in the smolt trap.

Stream Site n % Ripe Males

Scotts Creek Swanton 27 0.0%

Upper Scotts 36 2.8%

Big Creek 32 0.0%

Lower Scotts 15 0.0%

Soquel Creek Badger Springs 35 11.4%

Ashbury 51 5.9%

Girl Scout Falls 59 11.9%

Lion's Park 42 0.0%

Soquel Creek: Partial Barriers

Presumed resident steelhead from Soquel Creek.

This individual was age-2 at first capture, age-5 at last capture, and gained only 50mm over three years.

Ashbury Steelhead (2004-2006)PIT Tag: 15991573

0

20

40

60

80

100

120

140

160

Apr-04 Sep-04

Feb-05 Jul-05 Dec-05

May-06

Oct-06 Mar-07 Aug-07

Fo

rk L

eng

th (

mm

)

Ashbury Steelhead (2004-2006)PIT Tag: 15991573

0

5

10

15

20

25

30

35

Apr-04 Sep-04 Feb-05 Jul-05 Dec-05 May-06 Oct-06 Mar-07 Aug-07

Wei

ght (

g)

Mokelumne River adult O. mykiss; Presumed resident rainbow trout.

Mokelumne River "Adult" O. mykiss2006-2007

0

100

200

300

400

500

600

700

Dec-05 Mar-06 Jul-06 Oct-06 Jan-07 Apr-07 Aug-07 Nov-07

Date

Fo

rk L

eng

th (

mm

)

Results

• Central Valley steelhead populations were found to have much higher growth rates than coastal populations. Steelhead parr reach smolt size in only one year on the American and Mokelumne Rivers.

• Significant growth in Coastal California steelhead occurs mostly during winter and spring. Many fish actually lose weight over the summer and fall, when streamflow is very low. Temperatures do not appear to be limiting.

• Coastal juveniles will still emigrate downstream even after little to no growth for many months. However, most are emigrating to the lagoon for further growth before smolting.

• Lowest site on each coastal stream stands out as high growth site, somewhat similar to lagoons.

• Resident rainbow trout are common in the Mokelumne River, rare below barriers in the coastal streams.

• Seining in Soquel Creek Lagoon for PIT tagged emigrants from upstream sites

PIT tag antenna on Soquel Creek to record emigrants

Acoustic tagging wild steelhead/rainbow trout on Lower American River to track emigration/residency

Lab Growth Experiment

Treatment Schedule Treatment 1: Aug 1 – Sept 26Treatment 2: Sept 27 – Nov 22Treatment 3: Nov 23 – Jan 18Treatment 4: Jan 19 – Mar 16.

Figure 1A: Average GrowthColeman Strain

(Northern Central Valley)

0

50

100

150

200

250

Jun-

06

Aug-0

6

Oct-0

6

Dec-0

6

Feb-0

7

Apr-0

7

FL

(m

m) Treatment 1

Treatment 2

Treatment 3

Treatment 4

Low Ration

Figure 1B: Average GrowthScott Creek Strain

(Central California Coastal)

0

50

100

150

200

250F

L (m

m) Treatment 1

Treatment 2

Treatment 3

Treatment 4

Low Ration