Cramer Fish Sciences

June 11 - July 1, 2007, Summary Postcard No. 9 - Season Final Update

Caswell:

We concluded trapping for the season on June 22nd and the traps were removed on June 28th with the help of a boom truck that was supplied by South San Joaquin Irrigation District (Figure 1).  We are very thankful for the irrigation district and their staff's help this year as well as previous years.  We cleaned the traps shortly after removal and stored them at the Oakdale waste treatment plant.  We are always appreciative of the support from the staff at the treatment plant.

Figure 1. Caswell Rotary Screw Trap hoisted in the air by a boom truck during trap removal on June 28^th. [click on the photo for enlarged view]

A total of 64 juvenile Chinook salmon were captured at Caswell Memorial State Park from June 11^th through June 22^nd (last day sampled) (Figure 2); increasing the season total to 2,892 Chinook.  Daily catch ranged from 0 to 18 Chinook (Figure 3).  Individual fork lengths ranged from 63 mm to 106 mm with a mean length of 84 mm and mean weight of 6.7 grams during this sampling period. 

Figure 2. Chinook salmon smolt captured on June 17^th. [click on the photo for enlarged view]

Figure 3. Combined traps daily catch at Caswell State Park and river flow (cfs) at Ripon (RIP; CDEC Station)

For the season, the contribution of the total catch from each trap was 990 Chinook salmon juveniles from the north trap, 1,061 from the south trap, and 841 from the lower trap.  The lower trap captured 27 of the 64 juvenile Chinook salmon, yielding 42% of the total catch for the sampling period and 29% of the total catch for the season (Figure 4).

Figure 4. Total catch contributions by julian week of the north, south, and lower rotary screw traps at Caswell Memorial State Park (RM 8).  To date the lower trap has contributed 29% of the total catch.

One O. mykiss (fork length 230 mm; weight 117.1 g; smolt index 5) was captured on June 13^th in the lower rotary screw trap during this sampling period.  This brings the season total catch of O. mykiss to 23 fish.

No trap efficiency tests were conducted during the sampling period.  Furthermore, due to low catch numbers and reoccurring poor fish condition, no tagging operations were conducted during this sampling period.  Field technicians rated gill color (1 - pale to 5 - bright red) of all Chinook in Caswell RST catch, an important diagnostic of columnaris and other infections (Figure 3).

A summary of gill ratings can be found in Figure 5.  Field technicians observed a decline in fish condition during the previous sampling period.  Fish condition apparently improved thereafter and no additional mortalities were observed through the end of the season, although no catch was recorded on June 20^th.

Figure 5.  Chart showing average daily gill rating (1 - pale to 5 - bright red).

During this sampling period sixteen different incidental species were captured, including bluegill sunfish, brown bullhead, gold fish, green sunfish, golden shiner, hardhead, largemouth bass, western mosquitofish, prickly sculpin, Sacramento sucker, tuleperch, white catfish, white crappie, striped bass, smallmouth bass (Figure 6), spotted bass as well as unidentified bass and sunfish. 

Figure 6. Smallmouth bass (FL: 113 mm) captured in the lower trap on June 18^th. [click on the photo for enlarged view]

Coded Wire Tagging (CWT): 

Coded wire tagging of juvenile Chinook did not occur during this sampling period. To view the latest details of the coded wire tagging operations go to the Coded Wire Tagging Update #6.

Environmental Data: 

Instantaneous water temperature recorded at Caswell ranged from 61.6°F to 70.5°F.  Turbidity at Caswell ranged from 1.6 NTU to 4.1 NTU.  The supplemental Vernalis Adaptive Management Program (VAMP)scheduled flow reduction date was delayed several times to benefit the delta smelt (Hypomesus transpacificus), a Federal and State listed threatened species.   VAMP releases ended on June 11^th, thus Goodwin Dam (GDW) releases ranged from 352 cfs to 1,000 cfs.  Flows at Orange Blossom Bridge (OBB; RM 46.9) ranged from 535 cfs to 847 cfs and at Ripon (RIP; RM 15.8) from 432 cfs to 1,051 cfs. 

Click here if you need Adobe Acrobat Reader