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May 15
through May 28, 2006, Report No.
9
Oakdale:
The Oakdale rotary screw trap
sampled a total of eight out of 14 days between May 15 and
May 28. A total of 3,123 juvenile Chinook salmon were
captured, increasing the season total to 52,485 (Figure 1).
Daily catch ranged from 341 to 450 Chinook. Average
forklength was 87.7 mm and ranged from 34 mm to 130 mm.
Average weight for captured Chinook was 7.7 g and ranged
from 6.9 g to 8.4 g.
Figure 1. Chinook
Catch at Oakdale versus Stanislaus River flow at Orange Blossom Bridge
(OBB).
Figure 2. A
Chinook fry captured at the Oakdale rotary screw
trap on May 20, 2006.
Two young-of-the-year O.
mykiss were captured during the sampling period
increasing the season total to seven (Table 1).
Table 1. Biosampling data
collected on O. mykiss captured between May 15 and
May 28, 2006.
|
Location |
Date |
Species |
Forklength (mm) |
Weight |
Smolt Index |
|
Oakdale |
5/21/06 |
O. mykiss |
63 |
2.5 |
2 |
|
Oakdale |
5/23/06 |
O. mykiss |
45 |
1.2 |
2 |
Two trap efficiency tests were
conducted on May 19 at Oakdale using Chinook from Merced
River Hatchery and "wild" Chinook that were captured in the
trap. Resulting efficiencies were 5.2% and 5.6%,
respectively (Table 2).
Table 2. Trap efficiency
tests conducted at Oakdale between
May 15 and May 28,
2006.
|
Location |
Date |
Mark |
Stock |
Number released |
Number recaptured |
Mean Length @ Release(mm) |
Mean Length @ Recapture (mm) |
Estimated
Efficiency |
Flow
(cfs)
at OBB |
|
Oakdale |
5/19/06 |
BCG |
Hatchery |
538 |
28 |
81.6 |
82.3 |
5.2% |
3,997 |
|
Oakdale |
5/19/06 |
TCG |
Wild |
304 |
17 |
86.7 |
84.1 |
5.6% |
3,997 |
We removed the cone from
the Oakdale rotary screw trap on May 24 after
discovering some wear on the cone's shaft (Figure 3).
The shaft was repaired and the cone was re-installed on
June 2
Figure 3. Worn
shaft on the Oakdale rotary screw trap.
Caswell:
The Caswell rotary screw traps
sampled seven out of 14 days between May 15 and May 28. A
total of 116 juvenile Chinook salmon were captured,
increasing the season total to 962 (Figure 4). Daily catch
ranged from five to 26 Chinook. Average forklength was 93.5
mm and ranged from 82 mm to 110 mm. Average weight for
captured Chinook was 9.2 g and ranged from 7.8 g to 10.4 g.
Figure 4. Chinook
Catch at Caswell versus Stanislaus River flow at Ripon (RIP).
No O. mykiss
were captured during the sampling period.
Two trap efficiency tests were
conducted at Caswell on May 20 and May 24 using Chinook from
Merced River Hatchery with resulting efficiencies of 0.5%
and 0.9%, respectively (Table 3).
Table 3. Trap efficiency
tests conducted at Caswell between May 15 and May 28,
2006.
|
Location |
Date |
Mark |
Number released |
Number recaptured |
Mean Length @ Release(mm) |
Mean Length @ Recapture (mm) |
Estimated
Efficiency |
Flow (cfs)
at RIP |
|
Caswell |
5/20/06 |
CFP |
1,013 |
5 |
81.9 |
72.6 |
0.5% |
3,903 |
|
Caswell |
5/24/06 |
CFP |
1,099 |
10 |
86.5 |
74.4 |
0.9% |
3,797 |
Smolt Survival
Release:
The California Department of
Fish and Game released 75,000 coded-wired tagged (CWT)
Merced River Hatchery Chinook at Knight's Ferry on April 28
to evaluate survival in the lower Stanislaus River. Between
May 15 and May 28, a total of 191 CWT fish (daily range: 15
to 36) were recaptured at Oakdale (14.2
river miles downstream of release site; Figure 5) and only
three were recaptured at Caswell (45.7 river miles
downstream of release site; Figure 6) during the same
sampling period (note: catch scales between figures are not
the same).
Figure 5.
CWT Catch at Oakdale
versus Stanislaus River flow at Orange Blossom Bridge (OBB).
Figure 6.
CWT Catch at Caswell
versus Stanislaus River flow at Ripon (RIP).
Environmental Data:
IInstantaneous water
temperature fluctuated between 48.0°F and 54.0°F at Oakdale
and between 54.0°F and 56.3°F at Caswell. Turbidity ranged
from 0.9 NTU to 1.6 NTU at Oakdale and from 1.4 NTU to 3.1
NTU at Caswell. During the sampling period, releases from
Goodwin Dam (GDW) ranged between 3,143 cfs and 4,034 cfs.
Flows at Orange Blossom Bridge (OBB; RM 46.9) ranged from
3,056 cfs to 3,997 cfs and at Ripon (RIP; RM 15.8) from
3,439 cfs to 4,247 cfs.
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