The Presence of Juvenile Chinook Salmon Has Declined in the Past Three Surveys in the Month

StanislausRiver Salmonid Report 9/8/06 to 1/9/07

During the period of September 8, 2006 toJanuary 9, 2007, eightsnorkel surveys were conducted on the StanislausRiver from Goodwin dam to Orange Blossom Bridge Recreation Area.

The location of the slow site at Goodwin Dam was moved on July 5th 2006 upstream to the float tube pool. The change was made due to unsafe, high velocity conditions following gravel restoration activities. The area of the new site is the same as the original but the nature of the new site is significantly different. This has resulted in lower observed fish densities following the move.

Temperatures in the upper reaches (Goodwin –Knights Ferry) from September to January ranged from 12ºC to 10ºC respectively. Temperatures in the lower reaches (Lovers Leap-Orange Blossom) ranged from 15oC and 10oC over the same time period (figure 1).

Figure 1. Hourly temperatures from 9/7/2006 to 1/7/2007 in the Lower Stanislaus River From Goodwin Canyon to Honolulu Bar.

Flows ranged from 1200 to 1300 in September and most of October with the exception of several days where they were reduced to 500cfs for gravel restoration work below Goodwin Dam. Flows dropped to an average of 600cfs to improve spawning conditions and were raised again to an average of 900cfs for the remainder of the survey period (figure 2).

The presence of over summering juvenile Chinook salmon has declined to near zero in most sites. The majority of salmon were observedin Honolulu Bar and in the Goodwin Dam reach in September and October. Peak densities were found in Goodwin Dam with 2.4 fish/100m2observed on September 20th.

Newly emerged Chinook fry were first observed at Two Mile Bar on January 8th in the gravel addition site. A school of 115 fish were observed of which 55 fry were 0-40mm in length, and 60 fry were 40-60mm in length. On January 9th a school of 50 fry were observed at Orange Blossom at the fast site. Of these fry, 90 were 0-40mm in length, and 10 fry were 40-60mm in length.

Adult Chinook Salmon were first observed in late October at Goodwin and Two mile bar, and in November at Knights Ferry, Lovers Leap and Orange Blossom Bridge Recreation Area.Adult Salmon were observed spawning in the newly placed gravel in November.

1+ Steelhead densities have increased and remain relatively high (up to 12/100m2) at Goodwin Dam in both fast and slow velocity areas. Densities of 1+ remain constant at Two Mile Bar, Lovers Leap, Knights Ferry and Orange Blossom. Densities of 1+ steelhead have steadilydeclinedatHonolulu from 0.95fish/100m² in September to .2fish/100m² in January. Densities of 0+ Steelhead at Goodwin, Two Mile Bar and Knights Ferry have remained constant with little fluctuation. Lovers Leap, Honolulu and Orange Blossom 0+ Steelhead densities have all decreased over the survey period. Densities of 0+ at Lovers Leap decreased from 2.49fish/100m² on September 15th, to 1.3 fish/100m² on January 3rd. Orange Blossom 0+ densities decreased from 1.75fish/100m² on September 21st, to 1.14fish/100m² on January 3rd. Honolulu had the greatest decrease in 0+ Steelhead from 4.54 fish/100m² on September 21st, to 0.14fish/100m² on January 3rd.

Figure 2. Flows at OrangeBlossomBridge from 10/2006 to 1/2007.