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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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