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May 23 through June 5, 2005, Report No.
4
Chinook
A total of 189 natural
juvenile Chinook were captured at Grayson (RM 5) between May
23 and June 5 increasing the season total to 1,262. Daily
catch ranged from 3 to 36 Chinook (Figure 1). Average
forklength was 95 mm and ranged from 78 mm to 115 mm.
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. A total of 5 CWT fish were
captured at Grayson (RM 5) between May 23 and June 5
increasing the season total to 347 CWT fish. Daily catch
ranged between 0 and 1 CWT fish (Figure 2). Average
forklength was 103 mm and ranged from 95 mm to 113 mm.
Figure 2. CWT
Catch at Grayson versus flow at Modesto.
Other species
A total of 12 non-salmonid
species were captured in the traps during the sampling period
including bluegill, hardhead, inland silverside, lamprey,
largemouth bass, mosquito fish, red shiner, Sacramento
pikeminnow, Sacramento sucker, smallmouth bass, tule perch and
white catfish. Of these, white catfish (n = 9) were the most
abundant and were 44 mm to 145 mm in length.
The next most abundant non-salmonid
species was young-of-the-year
largemouth bass (n =6)
that measured between 24 mm and 40 mm. Daily catch of other
non-salmonids species ranged between 1 and 4 individuals.
Environmental Data
Environmental conditions
fluctuated throughout the sampling period as a result of
decreasing reservoir releases that began around the last week
of May. Reservoir releases were reduced once Don Pedro was no
longer encroached. Instantaneous temperature at Grayson
fluctuated between 54° F and 58° F and turbidity ranged from
1.7 NTU to 4.0 NTU. During the sampling period, flow at La
Grange Dam (LGN; RM 52.2) ranged between 4,494 cfs and 6,621
cfs. Flows at Modesto (MOD; RM 16.3) ranged from 4,498 cfs to
5,972 cfs.
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