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December
12 through December 25, 2005
Note: Data is preliminary and subject to revision. Data
presented in this report are only from the Vaki RiverWatcher and
numbers may increase after the data on the back up system is
analyzed and compared. Weir Update:
A total of 92 Chinook (daily
range: 2 to 27) passed upstream of the weir between December 12 and December 25 increasing the season total to 3,685
Chinook. Whereas, a total of 4,804 and 4,403 Chinook passed the
weir by the same date in 2003 and 2004, respectively.
Figure 1.
Photo series of a 940 mm (TL) red male Chinook going through the Vaki on
December 12, 2005.
No
O. mykiss were
observed passing the weir or in the daily snorkel surveys during
the sampling period. Other species observed included
striped bass, Sacramento
sucker
and Sacramento pikeminnow.
Flow on the Stanislaus River increased from 350 cfs to 900 cfs
on December 16 when the U.S. Bureau of Reclamation began
evacuating water from New Melones Reservoir for flood control
purposes. Flows were increased three more times between
December 19 and December 27 (1,500 cfs on December 19; 2,500 cfs
on December 23; 5,000 cfs on December 27) due to increased
reservoir inflow from several rain events.
Approximately 1,200 cfs is the maximum flow that the weir can
sample effectively without requiring 24-hour maintenance to keep
it afloat. Although the weir has not been tested at flows
greater than 1,200 cfs, we do not believe the weir would stay
above the water due to the increased velocities at flows greater
than 1,500-2,000 cfs. As soon as we were notified that
flows would increase to 1,500 cfs to evacuate the current water
entering New Melones Reservoir, we made the decision to allow
the weir to collapse (i.e., by flattening the resistance boards
and removing barrels that were placed under several of the
panels to aid in floatation at higher flows) in order to prevent
the weir from blowing out since more rain was in the forecast
and flows could easily be increased to over 2,000 cfs.
Currently, the weir (resistance panels and liveboxes) is
completely submerged and will not sample until flows decrease
below 1,000 cfs. All of the Vaki components were removed
from the site except for the scanner since it is protected by
the braces at the entrance to the livebox.
Figure 2.
Left -to-right: (top) Weir site at 900 cfs; weir site at
1,500 cfs; weir site at 2,500 cfs. (bottom) north bank at
2,500 cfs (note: orange webbing is the work area boundary);
debris on livebox at 900 cfs; metal computer box at 2,500 cfs.
Environmental conditions
fluctuated at the weir site during the sampling period (i.e.,
December 12 through December 19).
Daily instantaneous measurements of turbidity, DO, and water
temperature ranged between 0.6 and 2.2 NTU; 10.2 mg/L and
10.8 mg/L; and 48.3ºF and 52.2ºF, respectively. DO at Rough 'n
Ready Island (RRI) in the San Joaquin River's Deep Water Ship
Channel ranged from 5.1 mg/L to 7.2 mg/L and water temperature
ranged from 50.0ºF to 51.6ºF.
Trapping:
Two trapping events were
conducted at the Stanislaus weir during the sampling period and
a total of 17 Chinook were captured increasing the season total
to 324. The length of Chinook captured to date ranged from
450
mm to 1,025 mm (avg=751 mm). Fifty-seven percent of the Chinook
were female (185 Chinook), forty-two percent were male (137
Chinook), and less than one percent were unknown gender (2
Chinook). Twelve percent (38 Chinook) were grilse (<600 mm) and
five percent (15 Chinook) were ad-clipped.
Figure 3.
Photos taken of Chinook during trapping periods (left to right):
685 mm (TL) female Chinook; scales removed from 750 mm (TL)
female Chinook; head of 1,025 mm (TL) male Chinook. |
