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January 3-16, 2005, Report No.
1
As in previous years, three
rotary screw traps were installed in the Stanislaus River,
one at Oakdale (RM 40.1) on January 3 and two at Caswell (RM
8.6) on January 4-5. Sampling commenced immediately
following installation.
Oakdale:
A total of 8,478 juvenile
Chinook were captured between January 4 and January 16.
Daily catch ranged from 18 to 3,476 Chinook (Figure 1). A
high number of Chinook (6,554 or 77%) were captured during a
three-day period following a temporary increase in flow and
turbidity that was correlated with a rain event. Individual
forklengths primarily ranged from 29 mm to 49 mm and daily
mean lengths ranged from 34 mm to 36 mm. Average weight for
captured Chinook was 0.3 g. A 125 mm Chinook was also
captured on January 12 but was not included in the total
catch or in calculations for mean length or weight.
Two
O. mykiss were
captured on January 4 measuring 254 mm and 271 mm with
weights of 179.3 g and 167.4 g, respectively. Both
O. mykiss were
rated as smolts (SI 5) based on their appearance.
Figure 1. Chinook
Catch at Oakdale versus flow at Orange Blossom Bridge.
Trap efficiency releases were
conducted each night between January 11 and January 16 and
results of releases are presented in Table 1. Estimated
trap efficiencies are consistent with past year's data under
similar flow conditions and higher turbidities this year do
not seem to have had an effect on trap efficiency at
Oakdale.
Table 1. Release
and recapture data for trap efficiencies conducted at
Oakdale.
|
Date |
# Released |
# Recaptured |
Trap Efficiency |
Mean Length @ Release (mm) |
Mean Length @ Recapture (mm) |
Turbidity (NTU) |
Flow @ OBB* |
| 1/11/05 |
505 |
13 |
2.57% |
35.5 |
35.9 |
18.7 |
1266 |
| 1/12/05 |
620 |
84 |
13.6% |
34.4 |
35.4 |
22 |
334 |
| 1/13/05 |
362 |
62 |
17.1% |
34.7 |
34.3 |
13.4 |
297 |
| 1/14/05 |
455 |
151 |
33.2% |
34.5 |
34.3 |
9.9 |
277 |
| 1/15/05 |
547 |
113 |
20.7% |
36.1 |
34.4 |
6.4 |
274 |
| 1/16/05 |
540 |
170 |
31.5% |
34.3 |
34.7 |
5.3 |
271 |
*Flow data at time of release
at OBB rather than daily average flow.
Caswell:
A total of 924 juvenile
Chinook were captured between January 6 and January 16.
Daily catch ranged from 0 to 409 Chinook (Figure 2). A
majority of Chinook (851 or 90.0%) were captured during a
three-day period following a temporary increase in flow and
turbidity that was correlated with a rain event. Individual
forklengths ranged from 29 mm to 44 mm and daily mean
lengths ranged from 34 mm to 39 mm. Average weight for
captured Chinook was 0.3 g. A 91 mm Chinook was also
captured on January 13 but was not included in the total
catch or in calculations for mean length or weight.
No
O. mykiss were
captured during the sampling period.
Figure 2. Chinook
Catch at Caswell versus flow at Ripon.
Trap efficiency releases
were conducted each night between January 13 and January
15 and results of releases are presented in Table 2.
Estimated trap efficiencies are consistent with past
year's data under similar flow conditions and turbidity
does not seem to have had an effect on trap efficiency at
Caswell.
Table 2. Release
and recapture data for trap efficiencies conducted at
Caswell.
|
Date |
# Released |
# Recaptured |
Trap Efficiency |
Mean Length @ Release (mm) |
Mean Length @ Recapture (mm) |
Turbidity (NTU) |
Flow @ RIP |
| 1/13/05 |
99 |
16 |
16.2% |
32.2 |
36.1 |
27.5 |
637 |
| 1/14/05 |
168 |
28 |
16.7% |
34.1 |
34.3 |
18.1 |
441 |
| 1/15/05 |
85 |
17 |
20.0% |
34.5 |
34.2 |
10.8 |
384 |
Environmental Data:
Several rain events occurred
during the sampling period causing environmental conditions to
fluctuate. Instantaneous temperature fluctuated between 45°F
and 51°F
at both Oakdale and Caswell. Turbidity ranged from 5.1 NTU to
22 NTU at Oakdale and from 6.2 NTU to 27.5 NTU at Caswell.
During the sampling period, flow releases from GDW fluctuated
between 225 cfs and 249 cfs. Flows at Orange Blossom Bridge (OBB;
RM 46.9) ranged from 280 cfs to 815 cfs and at Ripon (RIP; RM
15.8) from 343 cfs to 974 cfs. The difference between the
flow released at GDW and the recorded values at OBB and RIP
was a result of run-off produced by rain events.
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