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April 18 through May 8, 2005, Report No.
2
Chinook
A total of 619 natural
juvenile Chinook were captured at Grayson between April 18
and May 8 increasing the season total to 659. Daily catch
ranged from 8 to 57 Chinook (Figure 1). Average forklength
was 89 mm and ranged from 64 mm to 112 mm. No
O.mykiss were
captured during the sampling period.
Figure 1. Chinook
Catch at Grayson versus flow at Modesto.
The California Department of
Fish and Game (CDFG) released approximately 75,000 coded-wire
tagged (CWT) Chinook from Merced River Hatchery (MRH) at La
Grange (RM 52.2) on April 18 to estimate smolt survival
through the lower Tuolumne River. CDFG also released a
control group consisting of approximately 25,000 CWT fish near
the mouth of the Tuolumne River at Old Fisherman's Club on
April 20.
A total of 314 CWT fish were
subsequently captured at Grayson (RM 5) between April 20 and
May 8. Daily catch ranged between 0 and 140 CWT fish (Figure
2). Average forklength was 83 mm and ranged from 71 mm
to 97 mm.
Figure 2. CWT
Catch at Grayson versus flow at Modesto.
Other species
A total of 11 non-salmonid
species were captured in the traps during the sampling period
including Bluegill, Channel catfish, Goldfish, Golden shiner,
Hitch, Lamprey, Inland silverside, Sacramento pikeminnow,
Smallmouth bass, Warmouth, and White catfish. Of these, White
catfish (n = 16)
were the most abundant and were 42 mm to 155 mm
in length.
The next most abundant non-salmonid
species was Bluegill (n =14) that measured between 30 mm and
184 mm. Daily catch of other non-salmonids species ranged
between 1 and 10 individuals.
Environmental Data
Environmental conditions
fluctuated throughout the sampling period as a result of
decreasing reservoir releases that began around the second
week of April once Don Pedro was no longer encroached.
Instantaneous temperature at Grayson fluctuated between
52° F and 59° F and turbidity ranged from 2.2 NTU to 14.4 NTU.
During the sampling period, flow at La Grange Dam (LGN; RM
52.2) ranged between 3,007 cfs and 4,097 cfs. Flows at
Modesto (MOD; RM 16.3) ranged from 3,196 cfs to 4,316 cfs.
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