Using Data on Threatened Steelhead to Effectively Manage Water Operations and Minimize Impacts
* Can existing steelhead monitoring data be used to reveal relationships between water operations and steelhead population attributes, and can this information be used to more effectively manage water operations?
Central Valley steelhead is a threatened species that constrains water operations in the Central Valley Project (CVP) in California. The CVP is near the southern extent of the range of steelhead. Juvenile steelhead spend an entire year or more in freshwater before emigrating to the ocean. Because of the need to protect and restore this species, Reclamation water operations are affected by the juvenile steelhead freshwater residence time throughout the entire year (Reclamation 2008). Water temperature, particularly during the summer, is a primary limiting factor for steelhead in California (McEwan 2001). Unlike the more abundant Chinook salmon, the lifecycle of steelhead does not lend itself to ease in monitoring. Spawning occurs during higher flows and lower water clarity, with juveniles using higher water velocities and emigrating at a larger size (Shapovalov and Taft 1954). These factors make capturing steelhead difficult, and because no commercial fishery exists, there are few coded wire tag monitoring opportunities. Therefore, the vast majority of steelhead data is collected coincidental to monitoring for Chinook salmon. Monitoring has been ongoing for over 30 years targeting Chinook salmon. This monitoring includes regular trawling surveys in the lower Sacramento and San Joaquin Rivers and in the Delta, beach seining throughout the Delta, rotary screw trapping in the tributary streams, and monitoring of fish salvaged at the CVP and State Water Project (SWP) Delta pumping facilities.
Projected increases in Central Valley water temperatures, as depicted in climate change models (Reclamation 2008), are likely to negatively affect steelhead. However, without current baseline information on effects of water operations on steelhead, there will be no
Need and Benefit
Threatened steelhead trout constrain Federal and State of California water operations, yet existing data on the species have not been adequately analyzed. These existing data likely contain valuable information that could be used to more effectively manage water operation for all affected species in the Central Valley of California. The National Oceanic and Atmospheric Administration (NOAA) Fisheries has developed criteria, often using data on Chinook salmon as a surrogate for steelhead trout, by which to operate the CVP and SWP. Existing steelhead data could be more effectively used to develop operational criteria that protect the species, while liberating water for other beneficial uses. The ongoing Bay Delta Conservation Plan (BDCP), to which Reclamation is devoting considerable resources, would benefit from the analyses conducted using this existing data. The BDCP is proposing considerable changes in water operations in an attempt to minimize the effects of climate change on operations so this is timely, needed, and could save considerable money.
McEwan, D. 2001. Central Valley Steelhead, pages 1-44 in Contributions to the biology of Central Valley salmonids. Fish Bulletin 179. California Department of Fish and Game.
Reclamation 2008. Biological Assessment on the Continued Long-term Operations of the Central Valley Project and the State Water Project. Bureau of Reclamation. Sacramento.
Shapovalov, L., and A. Taft. 1954. The Life Histories of the Steelhead Rainbow Trout (Salmo gairdneri gairdneri) and Silver Salmon (Oncorhynchus kisutch) With Special Reference to Waddell Creek, California, and Recommendations Regarding Their Management. California Department of Fish and Game. Fish Bulletin No. 98.
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