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Cramer Fish Sciences
April
30 - May 20, 2007, Summary Postcard No. 7
Caswell:
A total of 487 juvenile Chinook salmon were captured at
Caswell Memorial State Park between April 30th
and May 20th
increasing the season total to 2,504 Chinook. Daily
catch ranged from 6 to 35 Chinook. Individual fork
lengths ranged from 67 mm to 103 mm. Mean length for
captured Chinook during this sampling period was 82 mm and
mean weight was 6.0 grams (Figure 1).
Figure 1. Photo of a swimming juvenile Chinook salmon (O.
tshawytscha).
[click on the photo
for enlarged view]
The contribution of the season
total catch from each trap was 878 for the north trap,
905 for the south trap, and 721 for the lower trap.
The lower trap captured 134 of the 487 juvenile Chinook
salmon, yielding 28% of the total catch for the sampling
period and 29% of the total catch for the season (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.
Five 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.
|
Species |
Trap |
Date
|
Fork Length (mm) |
Total Length (mm) |
Weight (g) |
Smolt Indices |
|
O. mykiss |
Lower |
4/30/2007 |
201 |
214 |
80.0 |
5 |
|
O. mykiss |
Lower |
5/8/2007 |
247 |
267 |
119.9 |
5 |
|
O. mykiss |
Lower |
5/14/2007 |
210 |
225 |
94.1 |
5 |
|
O. mykiss |
Lower |
5/16/2007 |
210 |
225 |
84.3 |
5 |
|
O. mykiss |
South |
5/18/2007 |
230 |
245 |
103.3 |
5 |
No trap efficiency tests were conducted during the
sampling period. Catches were relatively low, and
our priority was to coded wire tag available fish (see
Coded Wire Tagging Update #6).
On May 11th, a channel catfish was captured
at Caswell with large black spots, appearing larger than
the typical black spots channel catfish exhibit.
Scott Foott of the
USFWS Fish Health Laboratory
reported that the black spots were consistent with a
trematode infection, where skin cells respond by
excreting melanin and forming a cyst around the
parasite. We also reported a red coloration at the
base of the pectoral fins which is consistent with a
systemic bacterial infection causing the endothelial
lining of the blood vessels to break down (Scott Foott,
personal communication) (Figure 3). Fish can
recover from both of these types of infections.
Figure 3. Photo of a channel catfish
(Ictalurus punctatus) captured on May 11th
(FL: 135mm).
[click on the photo for enlarged view]
During this sampling period thirteen different types of
incidental species were captured, including bluegill
sunfish, brown bullhead, channel catfish, green sunfish,
hardhead, inland silverside, Sacramento pikeminnow,
Sacramento sucker, threadfin shad, tuleperch, western
mosquitofish, white catfish, and unidentified lamprey.
Coded Wire Tagging (CWT):
Coded wire
tagging of juvenile Chinook did occur during this sampling
period and details are available in the
Coded Wire Tagging Update #6.
Environmental
Data:
Instantaneous water temperature taken at Caswell
ranged from 54.5°F to 59.9°F. Turbidity at Caswell
ranged from 1.4 NTU to 4.6 NTU. During the sampling
period, releases from Goodwin Dam (GDW) ranged from 1,497
cfs to 1,508 cfs. The supplemental releases for VAMP
were scheduled for ramp down on May 21st however
that date was postponed until further notice. Flows at
Orange Blossom Bridge (OBB; RM 46.9) ranged from 1,182 cfs
to 1,203 cfs and at Ripon (RIP; RM 15.8) from 1,371 cfs to
1,444 cfs (Figure 5).
Figure 5. Combined traps daily catch at Caswell State
Park and river flow (cfs) at Ripon (RIP; CDEC Station)
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