Figure 1. Measuring catch at the Calaveras River rotary screw trap at Shelton Road.

The Calaveras River rotary screw trap at Shelton Road (RM 28) was operated eleven days between April 24 and May 22 and a total of 41 O. mykiss were captured, increasing the season total to 662 (Figure 1). Of the O. mykiss captured, 40 were YOY (>100 mm) and rated as fry (n=1), parr (n=37), and silvery parr (n=2), and one was Age 1+ (100-299 mm), rated as smolt (n=1). Average forklengths and weights are provided for the O. mykiss in Table 1.

No Chinook salmon have been captured this season.

Instantaneous temperature recorded at the trap ranged from 51.9�F to 58.2�F, and turbidity ranged from 0.79 NTU to 3.95 NTU. Daily average combined flow from New Hogan Dam (NHG) and Cosgrove Creek (COS) fluctuated between 79 cfs and 213 cfs, and at Bellota (MRS) flow fluctuated between 14 cfs and 221 cfs (Figure 2).

No trap efficiency experiments were conducted during the reporting period.

Table 1. Biosampling data for O. mykiss captured at Shelton Road between April 25 and May 22, 2011. Parentheses indicate range.

Figure 3. Juvenile Chinook salmon captured in the Stanislaus River rotary screw trap at Oakdale.

The Stanislaus River rotary screw trap at Oakdale (RM 40) sampled continuously during the reporting period. A total of 75 juvenile Chinook salmon were captured, bringing the season total to 42,415. Daily catch of Chinook salmon ranged between 0 and 12 individuals (Figure 3). Average forklengths and weights of Chinook salmon are provided in Table 2 for the 75 Chinook that were measured. Most of the measured Chinook were smolts (n=71), but parr (n=4) were also recorded.  

No O.mykiss were captured during the reporting period. The season total remains at 21.

Table 2. Biosampling data for Chinook salmon and O. mykiss captured and measured at Oakdale between April 25 and May 22, 2011.

Instantaneous temperature recorded at the trap ranged from 48.9�F to 58.5�F, and turbidity ranged from 0.13 NTU to 3.98 NTU (Figure 5). Daily average flow at Goodwin Dam (GDW) increased from 1,998 cfs and 2,568 cfs, and flow at Ripon (RIP) ranged from 1,972 cfs to 2,520 cfs (Figure 4).

No trap efficiency experiments were conducted during the reporting period.

Figure 4. Daily Chinook salmon catch at Oakdale, and Stanislaus River flow recorded at Goodwin Dam (GDW) and Ripon (RIP) in 2011.

Figure 5. Daily Chinook salmon catch at Oakdale in relation to instantaneous turbidity recorded at the trap in 2011.

The Stanislaus River rotary screw trap at Caswell State Park (RM 8) sampled continuously during the reporting period and a total of 69 juvenile Chinook salmon were captured, increasing the season total to 540. Daily catch ranged between zero and eight Chinook salmon (Figure 6).

No O. mykiss were captured during the reporting period. The season total remains at one.

No trap efficiency experiments were conducted during the reporting period.

Instantaneous temperature recorded at the trap ranged from 52.2�F and 55.9�F, and turbidity ranged from 2.09 NTU to 5.65 NTU. Daily average flow at Ripon (RIP) ranged from to 1,972 cfs to 2,520 cfs.

Figure 6. Daily Chinook salmon catch at Caswell, and Stanislaus River flow recorded at Ripon (RIP) in 2011.

The Tuolumne River rotary screw trap at Waterford (RM 30) operated continuously during the reporting period. A total of 178 juvenile Chinook salmon were captured bringing the season total to 4,223. Daily catch ranged between zero and twenty-three Chinook. Average forklengths and weights are provided in Table 3 for 178 of the Chinook salmon. The majority of the measured Chinook were smolts (n=177), but a parr (n=1) were also recorded.

No O. mykiss were captured during this reporting period.

Table 3. Biosampling data for Chinook salmon captured and measured at Waterford between April 25 and May 22, 2011. Parentheses indicate range.

Instantaneous temperature taken at the trap ranged from 49.4�F to 54.4�F, and turbidity ranged from 0.35 NTU to 4.2 NTU. Daily average flow at La Grange (LGN) decreased from 5,780 cfs to 2,960 cfs (Figure 7).

No trap efficiency experiments were conducted during the reporting period.

Figure 7. Daily Chinook salmon catch at Waterford, and Tuolumne River flow recorded at La Grange (LGN) and Modesto (MOD) between December 1, 2010, and May 22, 2011.

The Tuolumne River rotary screw traps at Grayson (RM 5) sampled continuously during the reporting period and catch at Grayson continues to be higher than during the previous two years. A total of 100 Chinook salmon were captured, bringing the season total to 1,574. Average forklengths and weights of all Chinook salmon are provided in Table 4. The majority of the salmon were smolt (n=99), but one parr (n=1) was also observed.

No O. mykiss were captured during this reporting period.

Table 4. Biosampling data for Chinook salmon captured and measured at Grayson between April 25 and May 22, 2011. Parentheses indicate range.

Instantaneous temperature taken at the trap ranged from 53.1�F to 58.2�F, and turbidity ranged from 1.15 NTU to 6.69 NTU. Daily average flow at Modesto (MOD) decreased from 5,860 cfs to 3,270 cfs (Figure 8).

No trap efficiency experiments were conducted during the reporting period.

Figure 8. Daily Chinook salmon catch at Grayson, and Tuolumne River flow recorded at La Grange (LGN) and Modesto (MOD) between January 1 and May 22, 2011.

The Mokelumne River rotary screw trap at Vino Farms (RM 54) was sampled intermittently, and a total of 72 juvenile Chinook salmon were captured during the reporting period, bringing the season total to 29,622.

Average daily flow from Camanche Reservoir (CMN) decreased from 3,003 cfs to 2,100 cfs (Figure 9). Instantaneous temperature ranged from 50.9�F to 54.3�F, and instantaneous turbidity ranged between 2.18 NTU and 4.87 NTU.

A total of 36 O. mykiss were captured during the reporting period, increasing the season total to 52.  

Flow in the Merced River at Cressy (CRS; RM 52) fluctuated between 1,639 cfs and 2,984 cfs during reporting period. Flow at Stevinson (MST; RM 5) fluctuated between 1,469 cfs and 2,766 cfs (Figure 11). Water temperatures in the Merced River ranged from 53.6�F to 58.1�F at Cressy, and from 55.1�F to 60.4�F at Stevinson (Figure 12).

On April 5 the California Department of Fish and Game initiated Kodiak trawling on the San Joaquin River near Mossdale (i.e. the Mossdale Trawl). Twenty-four days of trawling (with between 6 and 15 tows per day) were conducted between April 24 and

Figure 13. An acoustic tag is surgically implanted in a juvenile Chinook salmon.

May 22. A total of 1,454 naturally spawned juvenile Chinook salmon were captured during the reporting period, increasing the season total to 1,479. A total 146 hatchery origin Chinook salmon were also captured during the reporting period. Daily catch ranged between 2 and 212 Chinook (Figure 14).

Releases of acoustic tagged Mokelumne River Hatchery steelhead smolts were also made during the reporting period for the Six-Year Acoustic Study being conducted by the US Bureau of Reclamation and Department of Water Resources as required by the NMFS 2009 Biological Opinion on the long-term operation of the State and Federal export facilities. The objective of the study is to examine the effect of flows, exports, and other project actions on the survival of steelhead smolts outmigrating from the San Joaquin River basin. Approximately 480 steelhead smolts were released at Durham Ferry during May 3-7 and an additional 480 steelhead smolts were released during May 17-21.  

Approximately 480 acoustic tagged salmon smolts were also released at Durham Ferry during May 17-21 for the VAMP smolt survival study (Figure 13).

During the reporting period, flow in the San Joaquin River at Vernalis decreased from 22,654 cfs to 10,049 cfs (Figure 15). Water temperature in the San Joaquin River ranged from 57.1�F to 64.3�F at Vernalis, from 58.1�F to 65.1�F at Mossdale, and from 59.7�F to 65.4�F at Rough 'n Ready Island (Figure 16). Average daily dissolved oxygen (DO) in the San Joaquin River fluctuated from 7.8 mg/L to 8.7 mg/L in the deep-water ship channel (measured at Rough 'n Ready Island), and from 8.1 mg/L to 9.3 mg/L at Mossdale (Figure 17).