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US Fish & Wildlife Service FieldNotes
REGION 8: Hatchery Plan Would Preserve Genetic Stocks of Delta Smelt 
Region 8, April 28, 2008

Bob Clarke, Asst. Fisheries Program Mgr. 
As populations of federally-threatened delta smelt decline in the Sacramento-San Joaquin River Delta, the U.S. Fish and Wildlife Service is looking to fish hatcheries to preserve genetic stocks in case the decline continues.

Delta smelt have been listed since 1993, and current population indexes are at all-time lows.  Such low indexes, combined with the fact that delta smelt are essentially annual fish that die after spawning, present the possibility that delta smelt could go extinct in the wild before efforts to restore the Delta can produce an environment favorable to recovery.  This has led the Service‚Äôs Region 8 Water and Fishery Resources Program to the concept of maintaining a genetic refugial population representative of the wild population for two specific purposes:

--Ensure there are fish available for reintroduction should the population in the wild go extinct; and,

--Provide a source of fish for supplementation of wild populations should supplementation become a desired recovery action

The new hatchery would be dedicated to maintaining a genetic refugial population of delta smelt reflective of the population in the wild and would be capable of supplying fish for reintroduction or supplementation. In addition, the new hatchery would be designed to be expandable to undertake propagation of additional species, such as longfin smelt, Sacramento splittail, or green sturgeon as needed.

Delta smelt are currently being propagated at the U.C. Davis Fish Conservation and Culture Laboratory (FCCL) in Byron, California. The FCCL has been propagating delta smelt for 15 years and currently raises fish to be used in research studies. This year, the FCCL began a program to use approximately 600 wild fish that were captured in 2006 to begin a genetic refugial population.

In addition to the U.C. Davis facility, the Service has a fledgling delta smelt program that was started in 2006 at the Livingston Stone National Fish Hatchery (LSNFH). The purpose of the program at Livingston Stone is to develop technical expertise within the Service to reliably propagate delta smelt in captivity.

While there are currently two facilities with delta smelt captive propagation programs, neither FCCL nor LS NFH are large enough to maintain the number of individual family groups necessary to ensure against genetic loss. In addition, neither facility has capability to expand to provide an adequate source of fish should supplementation or reintroduction become necessary recovery actions. As a result, the Region 8 Water and Fishery Resources Program is in the initial stages of planning for a new hatchery facility.

Delta smelt (Hypomesus transpacificus) are slender-bodied fish, about 2 to 3 inches long. They are in the Osmeridae family (smelts). They have a steely blue sheen on the sides and seem almost translucent. Smelts live together in schools and feed on zooplankton (small fishes and invertebrates).

Delta smelt are found only from the Suisun Bay upstream through the delta in Contra Costa, Sacramento, San Joaquin, Solano and Yolo counties in northern California.

For a large part of their one-year life span, delta smelt live along the freshwater edge of the mixing zone (saltwater-freshwater interface), where the salinity is approximately 2 parts per thousand. Shortly before spawning, adults migrate upstream from the brackish-water habitat associated with the mixing zone and disperse widely into river channels and tidally influenced backwater sloughs. They spawn in shallow, fresh or slightly brackish water upstream of the mixing zone.

Contact Info: Scott Flaherty, , Scott_Flaherty@fws.gov