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Cramer Fish Sciences
April
9 -
April 29, 2007, Summary
Postcard No. 6
Caswell:
A total of 1,036 juvenile Chinook salmon
were captured at Caswell Memorial State Park between April 9th
and April 29th
increasing the season total to 2,017 Chinook. Daily catch
ranged from 10 to 330 Chinook. Individual fork lengths ranged from
57 mm to 146 mm (Figure 1). Mean length for captured
Chinook during this sampling period was 76 mm and mean
weight was 4.7 grams.
Figure 1. Photo of three juvenile Chinook salmon (O.
tshawytscha) swimming. [click on the photo for
enlarged view]
The contribution of the season total catch for each trap
are 742 for the north trap, 688 for the south trap, and
587 for the lower trap. The lower trap captured
356 of the 1,036 juvenile Chinook salmon yielding 34% of the
total catch for the sampling period and 29% of the total
catch for the season thus far (Figure 2).
Figure 2. Total daily catch contributions of the north,
south, and lower rotary screw traps at Caswell Memorial State Park (RM
8) during this sampling period. To date the lower trap has contributed 29% of the total
catch.
Three O. mykiss
were captured in the rotary screw traps during this
sampling period (Table 1).
Table 1.
Species, trap
location, date, fork length, total length, weight, and smolt
index of captured O. mykiss at Caswell Memorial State Park (RM
8).
|
Species |
Trap |
Date |
Fork Length (mm) |
Total Length (mm) |
Weight (g) |
Smolt Indices |
|
O. mykiss |
North |
4/10/2007 |
204 |
217 |
79.4 |
5 |
|
O. mykiss |
North |
4/12/2007 |
227 |
244 |
94.1 |
5 |
|
O. mykiss |
North |
4/22/2007 |
200 |
216 |
94.1 |
5 |
Three trap efficiency
tests were conducted during the sample period.
Juvenile Chinook salmon with a dye mark or fin-clip were
released above the traps at night. Estimated trap
efficiency ranged between 13.0 % (at 560 cfs) and 2.4 %
(at 1,362 cfs) (Table 2).
Table 2. Trap efficiency
data for the North/South traps, Lower trap, and all the
traps combined at Caswell State Park (RM
8) and flow at Ripon (RIP; RM 15.8).
|
Date |
Mark |
#Released |
#Recaptured North/South Traps |
North/South Trap Efficiency |
#Recaptured Lower Trap |
Combined Traps Efficiency |
Fork Length Release (mm) |
Fork Length Recapture (mm) |
RIP Flow (cfs) |
|
April 13th |
Caudal Fin Pink |
23 |
3 |
13.0% |
0 |
13.0% |
75 |
73 |
560 |
|
April 23rd |
Caudal Fin Pink |
68 |
1 |
1.5% |
2 |
4.4% |
77 |
76 |
1,367 |
|
April 25th |
Upper Caudal Fin-clip |
83 |
2 |
2.4% |
1 |
3.6% |
77 |
78 |
1,362 |
|
|
Totals |
174 |
6 |
3.4% |
3 |
5.2% |
|
|
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During this sampling
period ten different types of incidental species were
captured, including: bluegill sunfish, brown bullhead,
goldfish, inland silverside,
Sacramento sucker, spotted bass, tuleperch, western mosquitofish, white catfish, and unidentified lamprey. (Figure
3).
Figure 3. Photo of a inland silverside
(M. beryllina) captured on April 12th (FL:
84mm). [click on the photo for
enlarged view]
Coded Wire Tagging (CWT):
Due to observed poor condition of Chinook in the traps and
resultant elevated mortality rate, the Coded Wire
Tagging was suspended during this sampling period until
consultation with California Department of Fish and Game (CDFG),
U. S. Fish and Wildlife Service (USFWS), and Bureau of
Reclamation (USBR) are completed. The poor condition
of Chinook was observed intermittently during this sampling
season and specimens are concurrently under analysis
by Scott Foott at
the regional
U. S. Fish and Wildlife Service Fish Health Laboratory.
The next CWT update will contain detailed information on the
results from this analysis.
Environmental
Data:
Instantaneous water
temperature taken at the Caswell rotary screw trap ranged
from 53.3°F to 59.6°F. Turbidity at Caswell ranged
from 1.7 NTU to 3.5 NTU. During the sampling period
releases from Goodwin Dam (GDW) ranged from 503 cfs to 1,507 cfs.
The increased releases from GDW serves to supplement flows
on the San Joaquin River at Vernalis to assist in the
Vernalis Adaptive Management Plan (VAMP). Flows at Orange Blossom Bridge (OBB; RM
46.9) ranged from 424 cfs to 1,199 cfs and at Ripon (RIP; RM
15.8) from 513 cfs to 1,389 cfs (Figure 4).
Figure 4. Combined traps daily catch at Caswell State
Park and river flow (cfs) at Ripon (RIP; CDEC Station)
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