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April 3
through April 16, 2006, Report No.
6
Oakdale:
The Oakdale trap sampled 11
out of 14 days between April 3 and April 16. A total of
2,496 juvenile Chinook salmon were captured, increasing the
season total to 46,875 (Figure 1). Daily catch ranged from
29 to 660 Chinook. Average forklength was 60.5 mm and
ranged from 32 mm to 98 mm. Average weight for captured
Chinook was 2.0 g and ranged from 1.6 g to 2.3 g.
Figure 1. Chinook
Catch at Oakdale versus Stanislaus River flow at Orange Blossom Bridge
(OBB).
Two
O. mykiss were
also captured in the rotary screw trap during this sample
period,
increasing the season total to four. Forklengths were 163
mm and 212 mm and respective weights were 49.5 g and 98.9 g.
Two trap efficiency tests were conducted at Oakdale (April
13
and April 14) with resulting efficiencies of 5.2% and
3.7%, respectively (Table 1).
Table 1. Trap efficiency
tests conducted at Oakdale between April 3 and April 16,
2004.
|
Location |
Date |
Mark |
Number released |
Number recaptured |
Mean Length @ Release(mm) |
Mean Length @ Recapture (mm) |
Estimated
Efficiency |
Flow
(cfs)
at OBB |
|
Oakdale |
4/13/06 |
CFG |
267 |
14 |
65.5 |
68.1 |
5.2% |
3,813 |
|
Oakdale |
4/14/06 |
CFG |
438 |
16 |
65.0 |
64.2 |
3.7% |
3,772 |
Caswell:
The Caswell traps sampled 7
out of 14 days between April 3 and April 16. A total of 110
juvenile Chinook salmon were captured, increasing the season
total to 700 (Figure 2). Daily catch ranged from 3 to 34
Chinook. Average forklength was 75.0 mm and ranged from 49
mm to 105 mm. Average weight for captured Chinook was 5.5 g
and ranged from 2.5 g to 7.4 g.
No O. mykiss
were captured during the sampling period.
No trap efficiency tests were conducted at Caswell during
the sample period due to low catch numbers.
Figure 2. Chinook
Catch at Caswell versus Stanislaus River flow at Ripon (RIP).
Due to recent changes in U.S.
Fish and Wildlife Service (FWS) policy regarding rotary
screw trap safety features, all screw traps
owned by the FWS were required to undergo safety
modifications. Therefore, the Caswell traps were removed and
safety modifications were made between April 4 and April
10. Safety improvements included adding the following: (1)
a shield to the shaft collar bolt; (2) a hinged shield to
cover the rear of the cone; (3) additional handrails and
chains; (4) a panel on the port side handrail; and (5) a
modified safety sign. To view a complete list and detailed
descriptions of the screw trap safety improvements
click here.
Figure 3.
Photos of safety improvements to the Caswell
rotary screw traps. From left to right and top
to bottom: (1) a shield to the shaft collar bolt; (2)
a hinged shield to cover the rear of the cone; (3a)
additional handrails and (3b) chains; (4) a panel on the
port side handrail; and (5) a modified safety sign.
Environmental Data:
Environmental conditions
fluctuated throughout the sampling period due to several
rain events and fluctuating river flows. Instantaneous
water temperature fluctuated between 50.0°F and 51.6°F at
Oakdale and between 49.0°F and 54.1°F at Caswell. Turbidity
ranged from 1.6 NTU to 20.1 NTU at Oakdale and from 4.3 NTU
to 8.1 NTU at Caswell. During the sampling period, releases
from Goodwin Dam (GDW) ranged between 3,039 cfs and 6,148
cfs. Flows at Orange Blossom Bridge (OBB; RM 46.9) ranged
from 3,328 cfs to 6,524 cfs and at Ripon (RIP; RM 15.8) from
3,394 cfs to 5,585 cfs.
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