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March 20 through April 2, 2006, Report No.
5
Waterford:
A total of 241 juvenile Chinook salmon were captured at
Waterford between March 20 and April 2, increasing the
season total to 7,999. Daily catch ranged from 2 to 34
Chinook (Figure 1). Average forklength was 54 mm and ranged
from 30 mm to 110 mm. Average weight was 3.4 g and ranged
from 0.3 g to 9.6 g.
Figure 1. Chinook
salmon catch at Waterford versus flow at La Grange (LGN).
One O. mykiss, forklength 249 mm,
was captured on April 2nd (Figure 2). The fish
was dead, and the carcass was brought back to our office,
labeled, and stored in our freezer for pickup by CDFG. The
fish likely expired as a result of temporary debris loading
in the trap. Although the trap was operating, passage
through the cone was partially blocked by logs and the
debris load in the livebox was heavy as a result of
fluctuating river flow.
Figure 2.
O. mykiss carcass
captured in the Waterford trap on April 2, 2006.
No trap efficiency tests were conducted at Waterford during
this sample period due to low catch numbers.
Grayson:
A total of 53 juvenile Chinook salmon were captured at
Grayson between March 20 and April 2, increasing the season
total to 1,367. Daily catch ranged from 1 to 16 Chinook
(Figure 3). Average forklength was 70.9 mm and ranged from
31 mm to 105 mm. Average weight was 4.8 g and ranged from
0.3 g to 13.9 g.
Figure 3.
Chinook salmon catch at Grayson versus flow at Modesto (MOD).
No O.
mykiss were captured in the rotary screw trap during
this sampling period.
No trap efficiency tests were conducted at Grayson during
this sample period due to low catch numbers.
Temporary Sampling Interruptions:
We
encountered temporary interruptions at both trapping
locations during the reporting period, most of which were
the result of the traps being stopped by logs. At Grayson
each trap was stopped and fished less than 75% of the
sampling day on 2 occasions (e.g., north trap on March 27
and 29; south trap on March 30 and April 2).
On April 1,
it was necessary to raise the overhead cable at Waterford by
a few feet to allow adequate distance between it and the
water surface to insure safe passage past our trapping site
by boaters. Total downtime was approximately 3 ½ hours.
On April 2, high river flows and heavy debris loading
resulted in temporary trap downtime at Grayson. Large logs
stopped both traps and damaged some of the screening on the
cone (Figure 4). Our field crew was able to remove all
debris, repair the damage to the screens, and sampling
resumed by mid-afternoon. Total downtime was approximately 2
hours for Grayson.
Figure 3.
Heavy debris, high flows, and trap damage at Grayson on
April 2, 2006.
Environmental Data:
Instantaneous water temperature ranged between 48.0°F and
51.0°F at Waterford, and between 49.0°F and 53.2°F at
Grayson. Turbidity fluctuated between 1.7 NTU and 5.02 NTU
at Waterford, and from 1.9 NTU to 19.9 NTU at Grayson.
During the sampling period, flows at La Grange ranged
between 3,654 cfs and 6,297 cfs, while flows at Modesto
ranged between 4,003 cfs and 7,114 cfs.
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