Transcript Growth Trajectories of Wild California Steelhead Parr David Swank , Will Satterthwaite

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.
•
American R.
Mokelumne R.
Scotts
Creek
Soquel
Creek
Scotts Creek
Soquel Creek
Legend
Soquel Creek Watershed
0
2
4
Kilometers
8
¸
Coastal Estuaries = Critical Nursery Habitat
Lower American River
Lower Mokelumne River
Monthly Mean Water Temperature
2006-2007
Soquel Creek
Scotts Creek
American River
Mokelumne River
20
18
Degrees (C)
16
14
12
10
8
6
4
May
July
September
November
January
March
May
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)
Mean +/- 95% CI Drift Density
Drift densities are higher in Central Valley streams
2200
1800
1400
1000
600
200
-200
Central Valley Coast
REGION
Growth Rate (mm/day) from PIT tag recaps
Growth Rate (mm/day)
1.2
1
0.8
0.6
0.4
0.2
0
Mokelumne
American
Scotts
Soquel
YOY Steelhead Growth - by Stream
300
Mean Fork Length (mm)
250
American R.
200
Mokelumne R.
Soquel Crk.
150
Scotts Crk
100
50
0
3-Mar
22-Apr
11-Jun
31-Jul
19-Sep
8-Nov
28-Dec
Average length over a year for steelhead parr in the four study
streams 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 com bined 2006-2007
All Periods combined 2006-2007
0.25
Growth Rate (mm/day)
Growth Rate (mm/day)
0.25
0.2
0.15
0.1
0.05
0.2
0.15
0.1
0.05
0
0
Ashbury
Swanton
Upper Scotts
Big Creek
Site
Scotts Creek
Lower Scotts
Badger
Springs
GS Falls
Site
Soquel Creek
Lion's Park
Growth among time periods – Scotts Creek
Swanton
Upper Scotts
Big Creek
Lower Scotts
0.3
Growth Rate (mm/day)
0.25
0.2
0.15
0.1
0.05
0
June-Sept
June-Dec
Sept-Dec
Dec-June
1 Year+
Period
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.
Growth among time periods – Soquel Creek
Ashbury
Badger Springs
GS Falls
Lion's Park
0.4
Growth Rate (mm/day)
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
June-Sept
June-Dec
Sept-Dec
Dec-June
1 Year+
Period
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.
Scotts Creek Smolt Trap Recaptures
190
Fork Length (mm)
170
150
130
110
90
70
50
May-06
Jul-06
Aug-06
Oct-06
Nov-06
Jan-07
Mar-07
Apr-07
Jun-07
Capture Date
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%
Badger Springs
35
11.4%
Ashbury
51
5.9%
Girl Scout Falls
59
11.9%
Lion's Park
42
0.0%
Soquel Creek
Soquel Creek:
Partial Barriers
Ashbury Steelhead (2004-2006)
PIT Tag: 15991573
Fork Length (mm)
160
140
120
100
80
60
Presumed resident
steelhead from Soquel
Creek.
40
20
0
Apr-04 Sep- Feb-05 Jul-05
04
Dec05
May- Oct-06 Mar-07 Aug06
07
Ashbury Steelhead (2004-2006)
PIT Tag: 15991573
35
Weight (g)
30
25
20
15
10
5
0
Apr-04 Sep-04 Feb-05 Jul-05 Dec-05 May-06 Oct-06 Mar-07 Aug-07
This individual was age-2
at first capture, age-5 at
last capture, and gained
only 50mm over three
years.
Mokelumne River
adult O. mykiss;
Presumed resident
rainbow trout.
Mokelumne River "Adult" O. mykiss
2006-2007
700
Fork Length (mm)
600
500
400
300
200
100
0
Dec-05
Mar-06
Jul-06
Oct-06
Jan-07
Date
Apr-07
Aug-07
Nov-07
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
Figure 1A: Average Growth
Coleman Strain
(Northern Central Valley)
Treatment Schedule
250
200
FL (mm)
Treatment 1
150
Treatment 2
Treatment 3
100
Treatment 4
Low Ration
50
A
pr
-0
7
7
b0
Fe
06
ec
D
-0
6
O
ct
ug
-0
6
A
Ju
n0
6
0
Figure 1B: Average Growth
Scott Creek Strain
(Central California Coastal)
250
200
Treatment 1
150
Treatment 2
Treatment 3
100
Treatment 4
Low Ration
50
pr
-0
7
A
7
b0
Fe
06
ec
D
-0
6
O
ct
ug
-0
6
A
n0
6
0
Ju
Aug 1 – Sept 26
Sept 27 – Nov 22
Nov 23 – Jan 18
Jan 19 – Mar 16.
FL (mm)
Treatment 1:
Treatment 2:
Treatment 3:
Treatment 4: