Figure 1. Sunrise at the Calaveras River rotary screw trap.

The Calaveras River rotary screw trap at Shelton Road (RM 28; Figure 1) was operated thirteen days between April 4 and April 24, 2011 and a total of 59 O. mykiss were captured, increasing the season total to 621. Of the O. mykiss captured, 49 were YOY (>100 mm) and rated as fry (n=26) and parr (n=23), and five were Age 1+ (100-299 mm) and were rated as silvery parr (n=1) and smolt (n=4). Average forklengths and weights are provided for 54 of the O. mykiss in Table 1.

No Chinook salmon have been captured this season.

Instantaneous temperature recorded at the trap ranged from 49.4�F to 61.7�F, and turbidity ranged from 0.83 NTU to 3.76 NTU. Daily average combined flows from New Hogan Dam (NHG) and Cosgrove Creek (COS) fluctuated between 23 cfs and 486 cfs, and at Bellota (MRS) flows fluctuated between 0 cfs and 632 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 4 and April 24, 2011. Parentheses indicate range.

The Stanislaus River rotary screw trap at Oakdale (RM 40)sampled continuously during the reporting period. A total of 102 juvenile Chinook salmon were captured, bringing the season total to 42,340. Daily catch of Chinook salmon ranged between 0 and 31 individuals. Average forklengths and weights of Chinook salmon are provided in Table 2 for the 101 Chinook that were measured. Most of the measured Chinook were smolts (n=48), but fry (n=25) and parr (n=28) were also recorded.

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

Instantaneous temperature recorded at the trap ranged from 49.1�F to 51.4�F, and turbidity ranged from 0.58 NTU to 7.68 NTU (Figure 4). Daily average flows at Goodwin Dam (GDW) increased from 1,310 cfs and 3,113 cfs, and flows at Ripon (RIP) ranged from 1,254 cfs to 2,883 cfs (Figure 3).

No trap efficiency experiments were conducted during the reporting period.

Figure 3. Daily Chinook salmon catch at Oakdale, and Stanislaus River flow recorded at Goodwin Dam (GDW) and Ripon (RIP) in 2011.

Figure 4. 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 28 juvenile Chinook salmon were captured, increasing the season total to 471. Daily catch ranged between zero and seven Chinook salmon (Figure 5).

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 52.3�F and 55.4�F, and turbidity ranged from 4.07 NTU to 10.40 NTU. Daily average flow at Ripon (RIP) ranged from to 1,254 cfs to 2,883 cfs.

Figure 5. Daily Chinook salmon catch at Caswell, and Stanislaus River flow recorded at Ripon (RIP) in 2011.

Figure 6. Chinook salmon captured in the Tuolumne River rotary screw trap at Waterford.

The Tuolumne River rotary screw trap at Waterford (RM 30) operated continuously during the reporting period. A total of 29 juvenile Chinook salmon fry were captured bringing the season total to 4,045. Daily catch ranged between zero and five Chinook (Figure 6). Average forklengths and weights are provided in Table 3 for 26 of the Chinook salmon. The majority of the measured Chinook were smolts (n=18), but fry (n=8) 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 4 and April 24, 2011. Parentheses indicate range.

Instantaneous temperature taken at the trap ranged from 48.9�F to 52.3�F, and turbidity ranged from 1.71 NTU to 4.51 NTU. Daily average flow at La Grange (LGN) decreased from 8,340 cfs to 6,120 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 April 24, 2011.

Figure 8. Chinook salmon captured in the Tuolumne River rotary screws trap at Grayson.

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 8 Chinook salmon were captured, bringing the season total to 1,474 (Figure 8). Average forklengths and weights of all Chinook salmon are provided in Table 4. Half the Chinook captured were rated as smolts (n=4), but fry (n=3) and parr (n=1) were 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 4 and April 24, 2011. Parentheses indicate range.

Instantaneous temperature taken at the trap ranged from 51.0�F to 55.4�F, and turbidity ranged from 1.68 NTU to 4.34 NTU. Daily average flows at Modesto (MOD) decreased from 7,950 cfs to 6,230 cfs (Figure 9).

No trap efficiency experiments were conducted during the reporting period.

Figure 9. Daily Chinook salmon catch at Grayson, and Tuolumne River flow recorded at La Grange (LGN) and Modesto (MOD) between January 1 and April 24, 2011.

The Mokelumne River rotary screw trap at Vino Farms (RM 54) was sampled intermittently, and a total of 113 juvenile Chinook salmon were captured during the reporting period, bringing the season total to 29,550.

Average daily flow from Camanche Reservoir (CMN) ranged from 2,990 cfs to 3,440 cfs (Figure 10). Instantaneous temperature ranged from 48.9�F to 51.3�F, and instantaneous turbidity ranged between 2.41 NTU and 4.35 NTU.

Seven O. mykiss was captured during the reporting period, increasing the season total count to sixteen.

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). Fifteen days (ten tows per day) of trawling were conductedbetween April 5 and April 24. A total of 25 juvenile Chinook salmon were captured. Catch ranged between 0 and 10 Chinook per 10 tows (Figure 12).  

During the reporting period, flow in the San Joaquin River at Vernalis decreased from 28,075 cfs to 23,067 (Figure 15). Water temperature in the San Joaquin River ranged from 56.7�F to 61.3�F at Vernalis, from 57.4�F to 62.1�F at Mossdale, and from 58.5�F to 63.1�F at Rough 'n Ready Island (Figure 16). Average daily dissolved oxygen (DO) in the San Joaquin River fluctuated from 7.2 mg/L to 9.0 mg/L in the deep water ship channel (measured at Rough 'n Ready Island), and from 7.8 mg/L to 9.4 mg/L at Mossdale (Figure 17).