There are four races of Chinook salmon (Fall, Late-Fall, Winter, Spring) utilizing the Sacramento-San Joaquin Delta Estuary of California. Each race is classified according to the time it returns to freshwater to spawn. Winter run (Endangered Species Act listed in 1994 and California Endangered Species Act listed in 1989) and spring run (ESA listed as endangered, 1998 and CESA listed as threatened, 1999) are two very important races requiring monitoring. Many of the goals and objectives of our monitoring activities focus on these two races. The objectives of the juvenile fish monitoring studies are:

  • Monitor the relative abundance and timing of juvenile chinook salmon and resident fish in 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 Estuary
  • Create a historic record of both native and non-native juvenile fishes in the delta
Gathering data to better manage delta fish populations.
Photo: USFWS
Trawling for smolts.
Photo: USFWS