February 12 through February 25, 2007

A total of 3 Chinook salmon passed upstream of the weir between February 12 and February 25 increasing the season total to 3,065. Total-lengths ranged from 689 mm to 861 mm (avg = 755 mm). Other fish species observed included 196 Sacramento suckerfish and one Striped Bass (Figure 1).

Figure 1. A striped bass (Morone saxatilis) and a group of Sacramento suckers (Catostomus occidentalis) passing through the Vaki RiverWatcher between February 12 - 25, 2007.

Zero ad-clipped Chinook salmon (i.e. indicating presence of coded wire tag) passed upstream of the weir during this sample period. We have observed a total of 61 (2.0%) ad-clipped Chinook salmon pass the weir this season.

Three fungus covered male Chinook salmon carcasses (TL: 690mm, 800mm, and 1,080mm) were recovered on top of the weir during this sample period.  All Chinook salmon carcasses were processed and then passed downstream over the weir.  

Two live O. mykiss passed the weir during this sample period; TL: 533mm and 554mm; bringing our season total of O. mykiss to pass the weir to 10.  Both of the O. mykiss that passed the weir were female and were not ad-clipped (Figure 2).

Figure 2. A female O. mykiss (TL: 554mm) passing through the Vaki on February 17 at 6:30pm.

One female O. mykiss (TL: 490mm) carcass and one male O. mykiss (TL: 445mm) carcass were found on top of the weir on February 21 and February 23, respectively (Figure 3). Our season total for O. mykiss carcasses found on the weir is now 6.

Figure 3.  Left: A female O. mykiss (TL: 490mm) recovered on February 21.  Right: A male O. mykiss (TL: 445mm) recovered on February 23.

The upstream livebox trap was closed one day during this sample period due to an increase in turbidity over 3 NTU.  No fish were captured in the trap on this day.  The trap was subsequently opened once turbidity fell below 3 NTU.

Environmental conditions varied at the weir site during the sample period due to flow release changes as well as rain storm events. Flow at Orange Blossom Bridge (OBB) ranged from 614 cfs to 994 cfs, and flow at Ripon (RIP) ranged from 763 cfs to 960 cfs. Releases from Goodwin Dam (GDW) were increased from 800 cfs to 1,200 cfs during this sample period. Turbidity ranged between 0.40 NTU and 5.09 NTU; and dissolved oxygen (DO) ranged between 11.33 mg/L and 12.64 mg/L. DO at Rough 'n Ready Island (RRI) in the San Joaquin River's Deep Water Ship Channel ranged from 7.41 mg/L to 9.51 mg/L. Daily instantaneous water temperature at the Stanislaus River Weir ranged from 49.3 ºF to 51.4ºF.

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