Stanislaus River Weir Update                                                                    October 6, 2005

September 19 through October 2, 2005
 

Weir Update:

A total of 126 Chinook passed upstream of the weir between September 19^th and October 2^nd increasing the season total to 133 Chinook (Figure 1).  Whereas, a total of 308 and 16 Chinook passed the weir by the same date in 2003 and 2004, respectively. Based on water temperature and dissolved oxygen (DO) records at Rough ‘n Ready Island (RRI; Figures 2 and 3), it appears that DO conditions in the Delta and lower San Joaquin River may account for higher Chinook abundance observed in September of 2003 and 2005.  Other species observed included striped bass, catfish sp., sunfish sp., carp, and black bass. 

Figure 1.  Series of photos taken by the Vaki RiverWatcher of a 760 mm female Chinook on September 29, 2005. 

Figure 2.  Daily average water temperature in the San Joaquin River at Rough 'n Ready Island (RRI), 2003-2005.

Figure 3.  Daily average DO in the San Joaquin River at Rough 'n Ready Island (RRI), 2003-2005.

Environmental conditions fluctuated at the weir site during the sampling period.  Flow was approximately 250 cfs until October 1^st when flow at Goodwin Dam increased by 100 cfs for fall fishery flows.  Daily instantaneous measurements of turbidity, DO, and water temperature ranged between 1.6 and 2.5 NTU; 8.5 mg/L and 9.6 mg/L; and 59.9ºF and 62.4ºF, respectively.  DO at Rough 'n Ready Island (RRI) in the San Joaquin River's Deep Water Ship Channel ranged from 4.9 mg/L to 6.3 mg/L and water temperature ranged from 69.3ºF to 71.0ºF.

Trapping:

The first trapping period of the season occurred from the morning of October 1^st to the morning of October 3^rd. During the trapping period, the livebox was checked twice per day (i.e., once in the morning and once in the evening).  Instantaneous water temperature was above 60ºF during all trap checks except during the morning check of October 3^rd.  When temperatures were too high to handle fish (range: 60.9ºF to 64.9ºF), the gate on the upstream end of the livebox was opened and a total of 10 fish (5 males, 3 females, and 2 unknowns) swam upstream of the weir.  On October 3^rd, one female Chinook was captured in the trap,  measured (725 mm FL; 775 mm TL), and released upstream in good condition (Figure 4).

Figure 4.  Collecting scale sample (left) and measuring depth (right) of 725 mm FL female Chinook captured in the trap on October 3.

Weir Vandalism:

The Vaki system sustained damage when vandals broke into the livebox over the weekend on two occasions.  Little data was compromised since we were trapping during both incidents.  The first incident occurred between 10 PM and 8 AM October 1-2.  Several wires were cut including the power cable to the yellow DU (back up unit), cable connecting the two plates of the new computer's scanner, and the power cord to the halogen light.  We were able to swap out the scanners between the two systems so that the "new system" (Vaki RiverWatcher) was running properly.  Although the halogen lights were damaged, there were still LED lights that provided light at night.  New cables are currently en route from Iceland and the compromised cords will be replaced as soon as the replacements arrive.  The second incident occurred between 7 PM and 8 AM October 2-3 when the chain securing the upstream door of the livebox was cut and the trap door was partially open upon arrival.  A thicker heavy-duty chain was purchased to secure the door closed during trapping periods.