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April 7 through
May 11 , 2008; Report No.
4
Waterford:
The trap sampled continuously between April 7 and May 11. A total of
508 juvenile Chinook salmon were captured during the
sampling period increasing the season total to 2,956. Daily catch ranged from zero to 33 Chinook (Figure
1). Average forklength was 81 mm and ranged from 34 mm to
99 mm. Average weight was 6.0 g and ranged from 0.3 g to
10.8 g.
An O. mykiss (261 mm; 181.5 g) was captured in the rotary screw trap
on April 16 increasing the season total to eight.
Figure 1. Chinook
salmon catch at Waterford versus flow at La Grange (LGN).
No
trap efficiency tests were conducted at Waterford due to insufficient numbers of Chinook captured during the sampling period.
Instantaneous water temperature taken at the Waterford trap
ranged between 54.5 °F and 69.9 °F and turbidity ranged from
0.9 NTU to 5.4 NTU. Daily average flow at La Grange ranged between
163 cfs and 1,310 cfs. Releases from La Grange Dam were increased during the VAMP period (i.e., between April 19 and May 19, 2008).
Grayson:
The traps sampled continuously between April 7and May 11. A total of 44 juvenile Chinook were captured increasing the season total to 179. Daily catch ranged from zero to six Chinook (Figure
2). Average forklength was 87.9 mm and ranged from 72 mm to
98 mm. Average weight was 7.2 g and ranged from 3.9 g to
9.4 g.
Figure 2. Chinook
salmon catch at Grayson versus flow at Modesto (MOD).
Three
trap efficiency tests were conducted at Grayson using fish from Merced River Hatchery on April 15, April 25, and May 7 with resulting efficiencies of 8.7%, 1.6%, and 1.5%, respectively (Table 1).
Table 1. Release and recapture data for trap efficiency
releases conducted at Grayson.
| Release Date |
# Released |
# Recaptured |
Trap Efficiency |
Mean at Release (mm) |
Mean at Recapture (mm) |
Flow at MOD (cfs) |
Turbidity (NTU) |
| 4/15/08 |
1,131 |
98 |
8.7% |
77 |
76 |
300 |
4.79 |
| 4/25/08 |
1,005 |
16 |
1.6% |
86 |
85 |
1,310 |
4.29 |
| 5/7/08 |
526 |
8 |
1.5% |
96 |
96 |
1,300 |
2.85 |
Instantaneous temperature taken at the trap ranged between 57.0 °F and 70.1 °F, and turbidity ranged from 1.8 NTU to 9.29 NTU. Daily average flow at Modesto (MOD) fluctuated between 288 cfs and 1,320 cfs. |
