Severe drought in California has reduced the Sacramento River to such low levels that officials are worried the state’s salmon won’t survive their spring migration. That’s why, starting later this month, young hatchery-raised salmon could be getting a little migratory help from the state.
Under a plan announced this week by state and federal officials, the state’s 30 million young hatchery-born fall-run Chinook salmon will be shipped via truck to the Pacific Ocean if water levels in the river are too low and the water too warm for the fish to complete their migration. That means the salmon will be packed into climate controlled, water-filled 18-wheelers and take an approximately three-hour ride from their hatcheries to San Pablo Bay. There, they’ll be submerged into the bay in netted pens where they’ll remain for a few hours to adjust to the temperature, light and salinity before being towed farther out into the bay and released into the outgoing tide.
Hatchery-raised salmon are shipped by truck to the ocean even in non-drought years, but if all 30 million salmon are shipped by truck this year, it would be about three times the amount of salmon usually shipped by truck. Harry Morse, Information Officer at the California Department of Fish and Wildlife, said each truck could transport about 130,000 young fish at a time, and that the department would be renting five trucks in addition to the one truck it owns for the project. The gas bill alone for the endeavor, he said, would likely be more than $100,000, and the trucks would be run almost daily from the end of March to the middle of June.
“This is a drought contingency plan,” Morse told Climate Progress. “What we’re looking at is trying to make sure we have the best conditions for the out-migrating little fish that will go with the highest chance of surviving and returning. If we get continued rain for the next month, month and a half, we may start trucking and then may start cutting back.”
California used to ship most of its hatchery-raised fish by truck during migration season to protect them from predators and pollution, but they cut back on the practice after studies showed that trucked salmon were more likely to stray from their home rivers when it comes time for their return migration from the ocean to spawn. Morse said the department has a thorough tracking system to limit straying as much as possible among the salmon population, and typically about 95 percent of the fish return to spawn in the same river they came from.
Peter Moyle, professor and associate director of the Center for Watershed Sciences at the University of California, Davis, said he thinks trucking hatchery-raised fish the best thing to do, especially in a drought situation. Moyle said that even in normal years, the high numbers of young hatchery-raised salmon released into California’s rivers compete with wild fish for food and space, and since regular feeding has made the hatchery salmon bigger than wild fish, they usually win. In addition, hatchery-raised fish aren’t as stream-savvy as wild fish, meaning that they’re more easily caught by predators.
“Hatchery fish, when released from the hatchery, are very ill-equipped for surviving in the wild. They even have smaller brains, because they never get a chance to exercise their mental facilities in those hatchery troughs,” Moyle told Climate Progress. “That’s why when you release these fish in the wild, especially in streams, they have very high mortality rates — hatchery fish that are released in the Sacramento River under normal conditions still have 90 percent mortality.”
The trucking plan could save California’s hatchery-raised Chinook salmon population, but other state fish may not be so lucky. Depleted streams are making migration difficult for the Coho Salmon, which is already endangered. This year’s drought has created fears of extinction for the Coho salmon, whose numbers hover only in the low thousands, and has prompted broad fishing bans in many of California’s rivers and streams.