Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

The CV drainage as a whole is estimated to have supported spring-run Chinook salmon
runs as large as 700,000 fish between the late 1880s and the 1940s (Brown, Moyle et al.
1994). Before construction of Friant Dam, nearly 50,000 adults were counted in the San
Joaquin River alone (Fry 1961). Following the completion of Friant Dam, the native
population from the San Joaquin River and its tributaries (i.e., the Stanislaus and
Mokelumne Rivers) was extirpated. Spring-run Chinook salmon no longer exist in the
American River due to the operation of Folsom Dam. Naturally spawning populations of
CV Chinook salmon currently are restricted to accessible reaches of the upper
Sacramento River, Antelope Creek, Battle Creek, Beegum Creek, Big Chico Creek, Butte
Creek, Clear Creek, Deer Creek, Feather River, Mill Creek, and Yuba River (CDFG
1998). Since 1969, the CV Chinook salmon ESU (excluding Feather River fish) has
displayed broad fluctuations in abundance ranging from 25,890 in 1982 to 1,403 in 1993
(CDFG unpublished data).
The average abundance for the ESU was 12,499 for the period of 1969 to 1979, 12,981
for the period of 1980 to 1990, and 6,542 for the period of 1991 to 2001. In 2003 and
2004, total run size for the ESU was 8,775 and 9,872 adults, respectively. These
averages are well above the 1991 to 2001 average.
Evaluating the ESU as a whole, however, masks significant changes that are occurring
among populations that comprise the ESU. For example, the mainstem Sacramento River
population has undergone a significant decline while the abundance of many tributary
populations increased. Average abundance of Sacramento River mainstem spring-run
Chinook salmon recently declined from a high of 12,107 for the period 1980 to 1990, to a
low of 609 for the period 1991 to 2001 (Good, Waples et al. 2005). Meanwhile, the
average abundance of Sacramento River tributary populations increased from a low of
1,227 to a high of 5,925 over the same periods.
According to Good et al. (2005), abundance time series data for Mill, Deer, and Butte
creeks spring-run Chinook salmon (updated through 2001) confirm that population
increases in the tributary populations seen in the 1990s have continued. During this
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