Baby salmon released in Californias American River

The chinook salmon population set a historic low in 2009, after two years of fishing closures imposed to protect the species.

Officials are tagging 25 percent of the fish they release to track their patterns and see if they return to the river.

Tags recovered from salmon in 2009 show that too few American River salmon are finding their way home — a phenomenon known as "straying.”

Scientists say it appears the salmon are losing one of their defining traits — their ability to find their birth river after three years in the ocean.

They’re also worried the salmon are breeding with fish from other rivers, which weakens their genetic identity and could harm the salmon that still manage to spawn naturally, outside the hatcheries.

"Some are always going to stray, but this high percentage of straying is a great concern to all the fishery agencies,” said Joseph Johnson, a Fish and Game senior environmental scientist.

Fishery managers began dumping young salmon into San Pablo Bay in 1995 to help them avoid predators, water pumps and other perils in the Sacramento-San Joaquin Delta as they make their way to the ocean.

The practice has helped increase the number of salmon available to ocean fishermen but probably contributes to straying, which threatens the species as a whole, Johnson said.

Some are worried that salmon released in the American River this week still face too many dangers in the Delta.

"In our opinion, the only thing saving the fishing industry right now is getting the fish around the Delta,” said Dick Pool, owner of Concord-based tackle manufacturer Pro-Troll Fishing Products and founder of water4fish.org, an advocacy group.