By Laila Kearney
SAN FRANCISCO, March 11 (Reuters) - California's record drought has left the Sacramento River so low that wildlife officials say they may have to carry all 30 million young salmon from the state's largest man-made hatcheries to the Pacific Ocean in trucks to avoid depleting the stock.
That is roughly three times the amount of salmon that are trucked out of the biggest hatcheries in a typical year, reflecting the severity of a drought that has prompted the governor to declare an emergency and warn of possible water shortages.
"This is not the course we normally take or prefer to take, but under these conditions, it presents us with the best way to get fish out there," said Steve Martarano, a spokesman for the federal Fish and Wildlife service.
California is in its third year of a dry spell that threatens to break all records in the most populous U.S. state, including possibly laying idle a half million acres of cropland, a loss of production that could cause billions of dollars in economic damage.
The vast majority of California's salmon come from four Sacramento River Basin-area hatcheries established to restore the state's salmon habitat, which was disrupted by construction of dams. A smaller number of salmon are born in hatcheries in the Klamath River system.
In a typical year, the California Department of Fish and Wildlife trucks about half of the 18.2 million salmon fry born in its three Sacramento River Basin hatcheries to the ocean.
The U.S. Fish and Wildlife Service, which runs the fourth Sacramento River Basin hatchery, rarely resorts to trucking its roughly 12 million young hatchery salmon.
The Klamath system, farther north in California, has seen more rainfall and has adequate water levels for fish migration that will not require mass salmon trucking, said Harry Morse, spokesman for the California Department of Fish and Wildlife.
Salmon are typically released from hatcheries into the Sacramento River and its tributaries between April and June to begin their migration into the Pacific Ocean, where they spend about three years before a small number of survivors begin their upstream run back to the hatcheries to spawn.
But this year water levels in the Sacramento River and its offshoots - the main passageways for California hatchery-spawned salmon out to sea - have dwindled to dangerously low levels.
The diminished habitat could mean a lack of food for the salmon, make them more visible to predators and raise water temperatures, which could be fatal for the fish, officials said.
Trucking the salmon to the ocean means loading the salmon onto 18-wheeler tanker trucks carrying river water kept below 60 degrees and driving up to five hours to the San Francisco Bay, where they are released into the bay in netted pens.
The fish are then towed out to sea in the pens, where they adjust to the ocean for about four hours before being released into open sea.
State and federal officials said they could abandon the plan if drought conditions are relieved by more wet weather.
Trucked salmon, which rely on their sense of smell to track their path from the ocean back to the hatcheries to spawn, are more likely to lose their way when returning. (Editing by Dan Whitcomb and G Crosse)