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September
6 through September 18, 2005
Weir Update:
The Stanislaus River weir was
installed between September 6th and September 8th
2005, in the same location as the previous three 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 April 2006.
A total of seven Chinook passed
upstream of the weir between September 12th and
September 18th. In the previous two years, only one
Chinook passed the weir by September 18th. Cooler
water temperatures and continually improving DO conditions in
the Delta and lower San Joaquin River may account for early
observations of Chinook this year. Other fish species observed
included striped bass, catfish sp., sunfish sp., carp, and black
bass.
Figure 1. A
735 mm female Chinook (left) and muskrat (right) passing the
weir on September 13 and 14, respectively. Note: lamprey
lacerations on the left side of the Chinook.
Environmental conditions at the
weir site remained stable throughout the sampling period. Flow
at Orange Blossom Bridge (OBB) was approximately 250 cfs,
turbidity ranged between 1.2 and 1.9 NTU, and dissolved oxygen
(DO) was approximately 10.0 mg/L. DO at Rough 'n Ready Island (RRI)
in the San Joaquin River's Deep Water Ship Channel ranged from
5.1 mg/L to 6.5 mg/L.
Daily instantaneous water
temperature at the weir ranged from 60.7ºF to 63.1ºF. Beginning
in October and when the water temperatures drop below 60ºF, we
will begin 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.
Livebox Modifications:
Prior to the 2005 season, major
modifications were made to the upstream livebox to improve the
quality of the photos taken by the Vaki RiverWatcher so that we
can more accurately distinguish between Chinook and
O. mykiss, and
determine sex and presence/absence of ad-clips. In 2004, we
were able to obtain photos for over 99% of the fish passing
through the Vaki RiverWatcher. However, a significant portion
of the photos were rated poor to fair based on fish orientation
to the camera. Often the fish were far away from the camera or
were at an angle not perpendicular to the camera. To resolve
this problem, a narrow "passing lane" measuring 18 inches wide
by 4 feet long was constructed out of acrylic to decrease the
distance away that the fish are allowed to pass in front of the
camera and to reduce the probability of the fish passing at an
angle (Figure 2). In addition, brackets on the camera were
modified to allow the camera to be positioned closer to the
passing lane and a second fyke was attached to the upstream end
of the passing lane to prevent fish from turning around and
"hanging out" in front of the camera once they pass through the
fyke.
Figure 2.
Photos of the passing lane (left), upstream fyke (middle), and
additional panels added to the livebox (right).
Other modifications included
fabricating a debris shield for the camera box and extending the
upstream end of the livebox by 3 feet to compensate for the
space lost from the addition of the passing lane (Figure 3).
The backup "yellow unit" was moved from the upstream end of the
livebox (i.e., at the exit) to a few inches in front of the Vaki
RiverWatcher scanner. This was done so that comparisons between
the two systems can be made during trapping periods. With the
previous setup, fish would only pass through one scanner (i.e.,
at the entrance of the livebox) during trapping periods and no
comparisons could be made between the two units to determine
their accuracy between each other and with what was trapped in
the livebox.
Figure 3.
Photos of livebox with attached camera box (left) and debris
deflector on camera box (right). |
