Young Chinook salmon abundance monitoring

Initial salmon work had occurred between 1974 and 1978, with a more comprehensive salmon program initiated in 1978. Field work entailed documenting the interannual and intraannual abundance and distribution for mainly fall run juvenile chinook salmon (beach seining in the lower Sacramento River, North and Central Delta between January and April, and midwater trawling at Sacramento and Chipps Island between April through June). Smolt survival in the Sacramento Delta using coded-wire tagged fish was also studied.

In 1989, the National Marine Fisheries Service listed winter run chinook salmon as threatened and as endangered in 1991. As part of the Biological Opinion, the CVP and SWP were directed to fund a juvenile salmon monitoring plan with emphasis on winter run. In October of 1991, DWR and USBR began funding the Sacramento/San Joaquin Estuary FRO to conduct the monitoring program to meet this need. Additional gears (fyke netting, pushnetting and rotary screw trapping) and year round sampling was initiated to better assess the distribution and relative abundance of all races of juvenile chinook salmon using the Delta and lower Sacramento River for rearing and as a migration corridor.

Our juvenile chinook monitoring program will continue to evolve and integrate into a valley wide juvenile salmon monitoring program. Our future focus on juvenile salmon and its problems will be more thoroughly integrated into the needs of salmon throughout the Central Valley as well as other aspects of the ecosystem as a whole.

Objectives:

• Monitor the relative abundance and timing of juvenile chinook salmon rearing and migrating through the Lower Sacramento River and Delta.

• Evaluate the significance of Delta fry rearing to overall production of the four races of chinook salmon.

• Determine the impacts of water development within the delta on the abundance, distribution and survival of juvenile salmon.

• Identify management measures that could lessen the impacts of water project operations on salmon migrating through and rearing in the

List of Species of Special Concern

• Chinook Salmon - Salmonidae, Oncorhynchus tshawytscha
  Four distinct races (runs), based on the time of year they re-enter fresh water to begin their spawning migration:
  1. Spring run
  2. Fall run (including San Joaquin Basin)
  3. Late-fall run
  4. Winter run - Federally listed as endangered
     State listed as endangered

• Delta Smelt - Osmeridae, Hypomesus transpacificus (incidental catch)
  Federally listed as threatened
  State listed as threatened

• Sacramento Splittail - Cyprinidae, Pogonichthys macrolepidotus (incidental catch)
  Proposed for federal listing as threatened

• Longfin Smelt - Osmeridae, Spirinchus thaleichthys (incidental catch)

Field Activities

• A weekly beach seining survey to estimate the relative inter and intra-annual abundance and distribution of all races of salmonid fry, using the Delta as a rearing and nursery area.

• A midwater trawl, kodiak trawl and fyke survey at Sacramento (beginning in September) to estimate the relative abundance and timing of fry and smolts entering the delta. Knowing when the various races and at what size they enter the Delta is helpful in managing water project protective criteria.

• Trawling conducted at Chipps Island, as in past years to estimate the number of unmarked fish emigrating from the Delta and to recover marked smolts released in our mark and recapture experiments
• Rotary Screw Traps.

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Recent Office Reports

USFWS-SSJFRO Chinook Salmon Monitoring Summary is updated weekly. This report lists the number of fall, late-fall, spring and winter run (based on size criteria, Fisher and Greene, April 1992) chinook salmon caught by each gear type. Coded wire tag releases and recoveries are also included in this report.

Abundance and Survival of Juvenile Chinook Salmon in the Sacramento-San Joaquin Estuary is published once per year. This report summarizes the office's results for each field season. The 1993 report was released in December 1994 and is now available.

Exhibit 7 - Testimony to State Board, July 1992

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For more information about this program element contact:
Mark Pierce, United States Fish and Wildlife Service
mpierce@delta.dfg.ca.gov