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

flow, temperature, sediment load, water quality, and channel stability are common
limiting factors in areas of critical habitat.
Sacramento River Winter­Run Chinook Salmon
Distribution
Sacramento River winter-run Chinook salmon consists of a single spawning population
that enters the Sacramento River and its tributaries in California from November to June
and spawns from late April to mid-August, with a peak from May to June (Figure 12).
Sacramento River winter Chinook salmon historically occupied cold, headwater streams,
such as the upper reaches of the Little Sacramento, McCloud, and lower Pit Rivers.
Life History
Winter-run fish spawn mainly in May and June in the upper mainstem of the Sacramento
River. Winter-run fish have characteristics of both stream- and ocean-type races. They
enter the river and migrate far upstream. Spawning is delayed for some time after river
entry. Young winter-run Chinook salmon, however migrate to sea in November and
December, after only four to seven months of river life (Burgner 1991).
Status and Trends
Sacramento River winter-run Chinook salmon were listed as endangered on January 4,
1994 (59 FR 440), and were reaffirmed as endangered on June 28, 2005 (70 FR 37160).
This was based on restricted access from dams to a small fraction of salmon historic
spawning habitat and the degraded conditions of remaining habitat. Sacramento River
winter-run Chinook salmon consist of a single self-sustaining population which is
entirely dependent upon the provision of suitably cool water from Shasta Reservoir
during periods of spawning, incubation, and rearing.
Construction of Shasta Dams in the 1940s eliminated access to historic spawning habitat
for winter-run Chinook salmon in the basin. Winter-run Chinook salmon were not
expected to survive this habitat alteration (Moffett 1949). However, cold water releases
from Shasta Dam have created conditions suitable for winter Chinook salmon for roughly
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