Stanislaus River Weir Monitoring continued with a total of 748 Chinook salmon passed upstream through the weir between October 1 and October 14, increasing the season total to 980.

Tuolumne River Weir Monitoring continued with a total of 493 Chinook salmon passed upstream through the weir between October 1 and October 14, increasing the season total to 551.

Mokelumne River Woodbridge Dam Fish Ladder Monitoring continued during the reporting period and a total of 961 Chinook passed upstream of the dam between October 1 and October 14.

San Joaquin Basin Escapement Surveys. Annual carcass surveys conducted by California Department of Fish and Game (CDFG) continued through the week of October 8.

San Joaquin River Conditions. San Joaquin River flow at Vernalis ranged from 960 cfs to 1,559 cfs. Daily average water temperature in the San Joaquin River ranged from 62.0�F to 72.5�F at Vernalis, and from 62.9�F to 73.8�F at Mossdale. Daily average dissolved oxygen (DO) in the San Joaquin River ranged from 8.3 mg/L to 9.6 mg/L at Mossdale, and from 6.2 mg/L to 7.2 mg/L in the deep-water ship channel (measured at Rough 'n Ready Island).

Between October 1 and October 14 a total of 748 Chinook salmon were detected by the Vaki Riverwatcher as they passed upstream of the Stanislaus River weir. The year-to-date total passage of 980 is the highest observed since 2003 (Figure 1; Table 1). Daily passage during the reporting period ranged between 8 and 143 Chinook salmon (Figure 2).

Instantaneous water temperature measured at the weir ranged between 55.9˚F and 63.9˚F, and daily average water temperature at Ripon (RPN; RM 15) ranged between 59.2˚F and 68.4˚F (Figure 3). Instantaneous turbidity ranged between 1.23 NTU and 4.52 NTU (Figure 4). Instantaneous dissolved oxygen at the weir ranged between 9.77 mg/L and 11.28 mg/L, and daily average dissolved oxygen at Ripon (RPN; RM 15) ranged from 8.23 mg/L to 9.87 mg/L (Figure 5).

Figure 4. Daily upstream Chinook passage at the Stanislaus River weir in relation to instantaneous turbidity recorded at the weir in 2012.

Fall-run Chinook salmon returning to the Mokelumne are counted annually by East Bay Municipal Utility District (EBMUD) as they ascend the fish ladder at Woodbridge Dam. A total of 961 Chinook salmon have been observed passing upstream of the dam so far this season. Daily passage ranged between 1 and 343 Chinook (Figure 11).

Figure 11. Daily upstream Chinook passage recorded at the Woodbridge Dam fish ladder in relation to daily average flows (cfs) recorded in the Mokelumne River at Camanche Reservoir (CMN), 2012. 

During the reporting period, flow in the San Joaquin River at Vernalis fluctuated from 960 cfs to 1,559 cfs (Figure 12). Water temperature in the San Joaquin River ranged from 62.0�F to 72.5�F at Vernalis, from 62.9�F to 73.8�F at Mossdale, and from 68.9�F to 74.4�F at Rough 'n Ready Island (Figure 13). Average daily dissolved oxygen (DO) in the San Joaquin River fluctuated from 6.2 mg/L to 7.2 mg/L in the deep-water ship channel (measured at Rough 'n Ready Island), and from 8.3 mg/L to 9.6 mg/L at Mossdale (Figure 14).

Figure 12. San Joaquin River flow at Vernalis from October 1, 2011, through October 14, 2012.

 

Figure 13. San Joaquin River daily average water temperature at Vernalis, Mossdale, and Rough 'n Ready from October 1, 2011, through October 14, 2012.

  

  

 

Figure 14. San Joaquin River daily average dissolved oxygen at Mossdale and Rough 'n Ready, from October 1, 2011, through October 14, 2012.