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April 18 through
May 8, 2005, Report No.
8
Oakdale
The Oakdale trap continued to
sample intermittently until April 29 when Goodwin Dam (GDW)
releases were increased to 1,500 cfs for the Vernalis
Adaptive Management Plan (VAMP).
During the VAMP period the trap will sample continuously
unless daily catch becomes consistently low and
environmental conditions are stable. A total of 510
juvenile Chinook were captured increasing the season total
to 187,572. Daily catch fluctuated throughout the sampling
period and ranged from 3 to 67 Chinook (Figure 1). Average
forklength was 77.2 mm and ranged from 55 mm to 102
mm. Average weight for captured Chinook was 5.4 g and ranged
from 2.0 g to 10.9 g.
No O.mykiss
were captured during the sampling period.
Average forklength increased
by almost 10 mm and average weight increased by almost 2.0 g
since the previous sampling period (i.e., April 4 to April
17). Low daily catch is characteristic at Oakdale during
this time of year when average fish size is within the range
of the parr lifestage (45mm-79 mm).
Figure 1. Chinook
Catch at Oakdale versus flow at Orange Blossom Bridge.
Due to low numbers of natural
Chinook, no trap efficiency releases were conducted during the
sampling period.
Caswell
The Caswell
traps continued to fish intermittently until April 29 when
GDW releases were increased to 1,500 cfs for VAMP. During
the VAMP period the traps will sample continuously unless
daily catch becomes consistently low and environmental
conditions are stable.
A total of 694
juvenile Chinook were captured increasing the season total
to 24,872.
Daily catch ranged from 8 to 150 Chinook (Figure 2) with a
small peak in catch associated with the initial increase in
flow due to VAMP releases.
Average forklength was 84.2 mm and ranged from
65 mm to 107 mm.
Average weight for captured Chinook was 7.6 g and
ranged from 3 g to 13.2 g.
Average forklength increased by less than 2 mm and
average weight increased by 1.0 g over the previous sampling
period (i.e.,
April 4 to April
17).
No O.mykiss
were captured during the sampling period.
Figure 2. Chinook
Catch at Caswell versus flow at Ripon.
No trap efficiency releases were conducted at Caswell during
the sampling period due to low catch of natural Chinook.
Environmental Data
Environmental conditions
fluctuated during the sampling period. Instantaneous
temperature fluctuated between 53° F and 57° F at
Oakdale and between 56° F and 64° F at Caswell. Turbidity
ranged from 1.2 NTU to 6.3 NTU at Oakdale and from 3.5 NTU to
9.2 NTU at Caswell. During the sampling period, flow releases
from GDW ranged between 400 cfs and 1,519 cfs. Releases from
GDW were increased from approximately 400 cfs to 1,500 cfs on
April 29 for VAMP and will remain at 1,500 cfs throughout the
VAMP period until May 29. Flows at Orange Blossom Bridge (OBB;
RM 46.9) ranged from 337 cfs to 1,331 cfs and Ripon (RIP; RM
15.8) ranged from 330 cfs to 1,522 cfs. As in past years,
flows observed at OBB are approximately 200 cfs lower than GDW
releases when flows are over 1,000 cfs.
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