SAN FRANCISCO -- The California Department of Fish and Game released an estimated 400,000 young Chinook salmon, called smolts, into the San Francisco Bay Monday, according to Fish and Game spokesman Harry Morse.

A total of about 17 million salmon smolts will be released over a two-month period that began in mid-April, Morse said.

The fish released today were 3 to 5 inches long and came from the Feather River Hatchery in Orville and the Nimbus Hatchery on the American River in Rancho Cordova.

They were transported to the bay in refrigerated tanker trucks. During the journey, salt was pumped into the trucks to get the young fish used to the saline levels found in the bay, Morse said.

Transporting smolts by truck helps reduce their contact with impassable barriers in rivers, their exposure to pollution and prevents them from getting lost or eaten by birds or other fish as they make their way to the ocean. The process and is believed to increase their survival rate by two to four times, according to Fish and Game officials.

But even when they are transported, less than one percent, or only about 320,000, are expected to return next year to spawn, Morse said.

Fish and Game officials began offloading the smolts through large tubes into acclamation pens off Mare Island at about 9 a.m.

The pens will protect the salmon while they adjust to the new environment.

"It's pitch black inside the tanker trucks and when they come out into the bright sunlight, they get really confused and go in all different directions," Morse said.

In their confusion, the smolts would be easy targets for birds and predatory fish.

As soon as they get their bearings, they drop down to the bottom of the pens, which are covered with wire mesh to keep birds out, Morse said.

He estimated that only about 20 to 50 of the young fish were carried away by birds Monday.

Once the fish had adjusted, tug boats from the contract company Fisheries Foundation of California towed the pens out into the bay and released the fish with the outgoing tide, Morse said.

The Department of Fish and Game has been trucking salmon from the hatcheries for release in the bay for the past 10 years, but this year they are taking additional precautions to help increase their survival rate.

Ordinarily, the department releases about half the smolts into the acclamation pens and the other half directly into the bay.

This year, with fish stocks at historically low numbers, they will be releasing all 17 million into the pens, Morse said.

Historically low salmon populations prompted the Pacific Fishery Management Council to cancel the six-month season for West Coast commercial and sport salmon fishermen, which was scheduled to begin May 1.

On Friday, the Fish and Game Commission voted to also cancel the fall salmon fishing season in California rivers, which was scheduled to run from Nov. 1 through Dec. 31.

Salmon fishing will be banned on the American River, Auburn Ravine Creek, Bear River, Coon Creek, Dry Creek, Feather River, Merced River, Mokelumne River, Napa River, San Joaquin River, Stanislaus River, Tuolumne River, Yuba River, and the Sacramento River.

A one-bag limit will be in place on the Sacramento River from Red Bluff Diversion Dam to Knights Landing for the fall season.

Morse said Fish and Game biologists were initially concerned about releasing the fish following an estimated 3,300-gallon spill of the toxic chemical solvent toluene in Richmond last week, but tests found only trace amounts of the chemical reached the bay.

The chemical, which was spilled into Parchester Marsh on the Point Pinole Regional Shoreline is believed to have killed about 400 fish and three mallard ducks as of Thursday. Updates on possible additional kills were not immediately available.