Figure 1. Stanislaus River weir.

Between October 11 and October 31 a total of 461 fall-run Chinook salmon were detected by the Vaki Riverwatcher as they passed upstream of the Stanislaus River weir, increasing the season total to 679 (Figures 1 and 2). Daily passage ranged from 7 to 50 Chinook salmon (Figure 4). The number of Chinook salmon passages observed so far this year is consistent with passages observed during this period in previous years (Table 1; Figure 3).

Figure 2. Rare sockeye/kokanee footage in the lower Stanislaus River. Read more on our Field Notes page.

Instantaneous water temperature measured at the weir ranged between 53.7˚F and 65.6˚F, and daily average water temperature at Ripon (RPN; RM 15) ranged between 56.1˚F and

67.2˚F (Figure 5). Instantaneous turbidity ranged between 0.60 NTU and 6.11 NTU (Figure 6). Instantaneous dissolved oxygen at the weir ranged between 8.32 mg/L and 9.51 mg/L, and daily average dissolved oxygen at Ripon (RPN; RM 15) ranged from 9.08 mg/L to 10.20 mg/L (Figure 7).

Daily average flows in the Stanislaus River at Goodwin Dam (GDW; RM 58) fluctuated between 203 cfs and 1,503 cfs due to regulated pulse flows. Similarly, flows at Ripon (RIP; RM 15) fluctuated between 209 cfs and 1,341 cfs (Figure 4). Note: flows downstream of Goodwin Dam may differ from dam releases due to irrigation, precipitation and other factors.

Figure 3. Cumulative passage of fall-run Chinook salmon recorded at the Stanislaus River weir from 2003-2010.

Figure 4. Daily upstream Chinook passage at the Stanislaus River weir in relation to daily average flows (cfs) recorded in the Stanislaus River at Goodwin (GDW) and Ripon (RIP), and in the San Joaquin River at Vernalis (VNS) in 2010.

 

 

Figure 5. Daily upstream Chinook passage recorded at the Stanislaus River weir in relation to instantaneous water temperature recorded at the weir, and daily average water temperature recorded in the Stanislaus River at Ripon (RPN) and in the San Joaquin River at Vernalis (VER), Mossdale (MSD) and Rough & Ready (RRI) in  2010.

Figure 6. Daily upstream Chinook passage at the Stanislaus River weir in relation to instantaneous turbidity recorded at the weir in 2010.

Figure 7. Daily upstream Chinook passage at the Stanislaus River weir in relation to instantaneous dissolved oxygen recorded at the weir, and daily average dissolved oxygen recorded in the Stanislaus River at Ripon (RPN), and in the San Joaquin River at Mossdale (MSD) and Rough & Ready (RRI) in 2010.

Figure 8. Stanislaus River rotary screw trap at Oakdale.

The Stanislaus River rotary screw trap at Oakdale (RM 40)was installed to monitor potential yearling Chinook migration during the fall pulse flow occurring from October 14 to October 29 (Figure 8). The trap operated continuously from October 11 and captured only three Chinook salmon (Figure 9). Two Oncorhynchus mykiss were also captured and measurements were collected for one of these individuals (Table 2).

Figure 9. Daily Chinook salmon catch at Oakdale, and Stanislaus River flow recorded at Goodwin Dam (GDW) and Ripon (RIP) in 2010.

Table 2. Biosampling data for Chinook salmon and O. mykiss captured and measured at Oakdale between October 11 and November 1, 2010.

Figure 10. Black bass captured in the Oakdale rotary screw trap. Read more on black bass captured at Oakdale on our Field Notes page.

 Rotary screw trap catch during this sampling period was dominated by black bass (genus Micropterus). A total of 366 small black bass were captured during the sampling period, including 274 that were positively identified as largemouth bass. The peak catch of black bass occurred just after the fall pulse flow began (Figure 10). Since the rotary screw trap was installed earlier than usual, historical data are not available for comparison.

Figure 11. Tuolumne River weir.

Between October 11 and October 31 a total of 324 Chinook salmon were detected by the Vaki Riverwatcher as they passed upstream of the Tuolumne River weir, increasing the season total to 487 (Figures 11). Daily passage ranged from 3 to 26 Chinook (Figure 12 and 14). The number of Chinook passages observed so far this year has exceeded the total passage count observed last year (Table 3; Figure 13).

Figure 12. Chinook salmon observed in the Tuolumne River.

Instantaneous water temperature measured at the weir ranged between 55.7˚F and 62.0˚F. Daily average water temperature at Modesto (MOD; RM 17) fluctuated between 57.2˚F and 61.2˚F (Figure 15). Instantaneous turbidity ranged between 0.41 NTU and 1.94 NTU (Figure 16), and instantaneous dissolved oxygen ranged between 7.47 mg/L and 9.37 mg/L (Figure 17).

Daily average flows in the Tuolumne River decreased from 858 cfs to 357 cfs at La Grange (LGN; RM 50) and from 968 cfs to 431 cfs at Modesto (MOD; RM 17) (Figure 18). Note: flows downstream of La Grange may be higher than dam releases due to accretion and Dry Creek inflow.

Figure 13. Cumulative passage of fall-run Chinook salmon recorded at the Tuolumne River weir in 2009 and 2010.

Figure 14. Daily upstream Chinook passage at the Tuolumne River weir in relation to daily average flows (cfs) recorded in the Tuolumne River at La Grange (LGN) and Modesto (MOD), and in the San Joaquin River at Vernalis (VNS) in 2010.

 

Figure 15. Daily upstream Chinook passage at the Tuolumne River weir in relation to instantaneous water temperature recorded at the weir, and daily average water temperature recorded in the Tuolumne River at Modesto (MOD), and in the San Joaquin River at Vernalis (VER), Mossdale (MSD) and Rough & Ready (RRI) in 2010.

 

Figure 16. Daily upstream Chinook passage at the Tuolumne River weir in relation to instantaneous turbidity recorded at the weir in 2010.

Figure 17. Daily upstream Chinook passage at the Tuolumne River weir in relation to instantaneous dissolved oxygen recorded at the weir, and daily average dissolved oxygen recorded in the San Joaquin River at Mossdale (MSD) and Rough & Ready (RRI) in 2010.

Annual carcass surveys conducted by California Department of Fish and Game (CDFG) continued during the week of October 25. The largest number of live fish was observed on the Tuolumne River, with a peak live count thus far of 71 Chinook. Peak live counts on the Stanislaus River have increased to 49, while the Merced rivers counts are still low, at 8 Chinook.

Twenty-two redds were observed on both the Stanislaus and Tuolumne rivers and two redds have been recorded on the Merced River. Typically, the peak number of redds observed for the fall-run season occurs in mid- to late-November.