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September
6 through September 24, 2006
The Stanislaus River weir was
installed between September 6th and September 8th
2006, in the same location as the previous four years, i.e.,
approximately two river miles below Jacob Meyer’s Park (RM 31.4)
near the town of Riverbank. Monitoring began immediately
following installation on the afternoon of September 8th
and will continue through June 2007.
We would like to thank the Department of Water Resources for
assisting us with the weir installation for the second time in
three years.
Figure 1. Fish Sciences installing the
Stanislaus River Weir with assistance from the Department of
Water Resources on September 6, 2006.
A total of 48 Chinook passed
upstream of the weir between September 9 and September 24.
Daily Chinook passage counts ranged from one to six. Other fish species observed
included
striped bass, catfish sp.,
Sacramento blackfish, Sacramento pikeminnow, Sacramento sucker,
goldfish, carp, and black bass
(Figure 2).
Figure 2. Photos from left to right: (top)
day photo of Chinook (764 mm; male); night photo of Chinook (700
mm; male); striped bass; (bottom) carp; Sacramento pikeminnow;
Sacramento sucker.
The first
O. mykiss (336
mm; unknown sex) of the season passed the weir on
September 24
(Figure 3). Based on the successful modifications to the
livebox last season, we are confident that we can continue to
distinguish
O. mykiss from Chinook.
Figure 3. A 336 mm O. mykiss
passing the weir on September 24, 2006.
Between September 6 and September
9, releases from Goodwin Dam (GDW) were reduced to 300 cfs to
allow adequate depth for installation of the Stanislaus River
weir. Following installation of the weir, releases at GDW
were increased to 1,200 cfs until September 19 when flows were
increased to 1,500 cfs. The highest flow under which the
Stanislaus River weir operated in previous years was 1,200 cfs
and that was only on a limited basis (i.e., 5 to 11 days) during
fall attraction flows. Currently, the Stanislaus River
weir is operating well with the exception of a few days during
the week of September 18th when we experienced heavy winds,
causing leafy debris to pile up on the weir panels (Figure 4). During this time, we increased the
frequency of cleaning in order to keep the weir afloat.
Figure 4. Stanislaus
River weir operating under 1,500 cfs on September 20, 2006.
Although, the
weir is functioning at this time, we are unsure of how well we
will be able to keep up with increased debris as more leaves
begin falling from the trees later in the season if the flow
remains high.
Environmental conditions fluctuated at the weir site during the sampling period. Flow
at Orange Blossom Bridge (OBB) ranged from 473 cfs to 1,289 cfs;
turbidity ranged between 0.4 NTU and 3.5 NTU; and dissolved oxygen
(DO) ranged between 9.0 mg/L and 10.3 mg/L. DO at Rough 'n Ready Island (RRI)
in the San Joaquin River's Deep Water Ship Channel ranged from
6.4 mg/L to 8.5 mg/L.
Daily instantaneous water
temperature at the Stanislaus River weir ranged from 55.2ºF to 61.7ºF.
Although, temperatures have been consistently below 60ºF (i.e.,
the maximum temperature at which we are permitted to handle
salmonids) since September 11, trapping will be postponed until
Chinook passage increases and flows decrease. At the
current flow, the water depth is too high to process the trap.
Once trapping commences, we will be trapping on a "two days on two days off" schedule to
collect biological data and to continue to test the accuracy of
the Vaki RiverWatcher system.
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