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DCC - Delta Cross Channel
The Delta Cross Channel (DCC) was constructed in 1951 to assist in transferring fresh water from the Sacramento River
across the Delta (DWR 1993). Flow from the Sacramento River into the DCC is controlled by two radial arm gates located
at the Sacramento River end of the DCC. These gates can be opened and closed depending on water quality, flood protection,
and fish protection requirements. Adult Chinook salmon (Oncorhynchus tshawytscha) are known to use the Sacramento River, DCC,
and Georgiana Slough as migration pathways (Hallock et al. 1970). When the DCC gates are open, Sacramento River water is
diverted into the Mokelumne and San Joaquin Rivers. Juvenile salmonids imprint on natal waters prior to and during emigration,
allowing them to return to their stream of origin as adults (Hasler and Scholz 1983, Dittman et al. 1994). Therefore, some
adult Chinook salmon returning to the Sacramento River system may be attracted into the San Joaquin and Mokelumne Rivers by
diverted Sacramento River water, possibly increasing the chance of straying or delayed migration (since using either or both
of these rivers is less direct than the Sacramento River). It is also possible that migrating adults using the DCC could be
blocked if the DCC gates are closed after the fish have been attracted into the DCC. Major delays in migration, blocked passage,
or straying of adult Chinook salmon could negatively affect spawning success.
To assess possible effects of DCC gate operations
on migrating adult Chinook salmon, the U.S. Geological Survey (USGS), U.S. Bureau of Reclamation (USBR), California Department of
Fish and Game (DFG), and the U.S. Fish and Wildlife Service (FWS) collaborated on a pilot study in 2000. The purpose of this pilot
study was to compare abundance and migration timing of adult Chinook salmon in the Sacramento River, DCC, and Georgiana Slough with
the DCC gates open and closed using hydroacoustic, sonic tagging, and fyke trap data. The pilot study was expanded in 2001 by
increasing sampling effort and duration. (to be continued)
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