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October
31 through November 13, 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 1,182 Chinook (daily
range: 12 to 420) passed upstream of the weir between October 31
and November 13 increasing the season total to 2,836
Chinook. Whereas, a total of 3,538 and 3,673 Chinook passed the
weir by the same date in 2003 and 2004, respectively. A peak in
Chinook passage (i.e., 420 fish) was observed on November 7 and
was not correlated to any known environmental factors. A
similar peak in passage was observed in 2003 and 2004 during
early to mid-November. No
O. mykiss were observed passing the weir or in the
daily snorkel surveys during the sampling period. Other species
observed included Sacramento sucker and Sacramento pikeminnow.
Figure 1.
Photos taken by Vaki RiverWatcher during the sampling period:
916 mm male Chinook (left), 483 mm grilse Chinook (middle), and
adipose fin clipped Chinook (right-front).
Environmental conditions
fluctuated at the weir site during the sampling period.
Releases from Goodwin Dam fluctuated between 350 cfs and 355 cfs.
Daily instantaneous measurements of turbidity, DO, and water
temperature ranged between 0.7 and 2.7 NTU; 9.5 mg/L and 10.6
mg/L; and 52.6ºF and 55.4ºF, respectively. DO at Rough 'n Ready
Island (RRI) in the San Joaquin River's Deep Water Ship Channel
ranged from 7.4 mg/L to 7.9 mg/L and water temperature ranged
from 58.3ºF to 61.5ºF.
An increase in turbidity occurred
between November 7 and November 10 (range: 1.7 - 2.7 NTU) and
was associated with a pipe spilling water into the Stanislaus
River approximately 1/2 mile above the weir (Figure 2). The
pipe was traced to its terminus using aerial photos which
indicated that water was likely coming from Modesto Irrigation
District’s (MID) irrigation canals originating from Modesto
Reservoir. Although turbidity cleared up within the first few
days, water continued to spill from the pipeline throughout the
remainder of the sampling period.
Figure 2.
Water spilling from MID irrigation pipe approximately 1/2 mile
upstream of the Stanislaus River weir.
Trapping:
Five trapping events were
conducted at the Stanislaus weir during the sampling period and
a total of 130 Chinook were captured increasing the season total
to 229. The length of Chinook captured to date ranged from
470
mm to 1,080 mm (avg=786 mm). Fifty-seven percent of the Chinook
were female (130 Chinook), forty-two percent were male (97
Chinook), and one percent were unknown (2 Chinook). Eleven
percent (24 Chinook) were grilse (<600 mm) and five percent (11
Chinook) were ad-clipped.
Figure 3.
Photos taken of Chinook during trapping periods. Top: Scale
samples obtained from a 1,025 mm male Chinook (left), measuring
a 945 mm Chinook (middle), measuring a 920 mm Chinook (right);
bottom: possible seal bites on underside of Chinook (left), 450
mm grilse female Chinook (middle), measuring a 670 mm female
Chinook (right). |
