April 11, 2014 — Three hundred thousand juvenile chinook with tiny coded chips lodged in their heads were released in Rio Vista and under the Golden Gate Bridge over the past two days in an experiment to determine optimal conditions for hatchery-raised salmon to survive and imprint on their native rivers.
The 6-month-old, pinkie-size fish from the Feather River hatchery near Oroville (Butte County) were separated into three groups of 100,000 and subjected to widely varying conditions before the release to see which method best helped the fish survive in the wild.
Biologists with the California Department of Fish and Wildlife are focusing mainly on the group that was loaded Tuesday into the hold of a fishing boat in the delta town of Rio Vista and transported down the Sacramento River to the Golden Gate, where they were released Wednesday.
That group of smolts swam through freshwater, brackish water and salt water that was circulated through the hold of the boat as they traveled from the Sacramento-San Joaquin River Delta downriver to the bay.
"The fish taste the water all the way down their migratory route and hopefully they are imprinting," said Heather McIntire, a senior environmental scientist for the Department of Fish and Wildlife.
The idea is to compare the survival and return rates of these salmon with fish that were trucked from the hatchery to San Francisco and a group of smolts released into the river at Rio Vista.
Read the full story from the San Francisco Chronicle