Salmon Stranded by Drought May Carpool to the Ocean in Massive Tanker Trucks

About 30 million fish are expected to hitch their way to the sea.

Chum salmon in flight.

(Photo: Daniel J. Cox/Getty Images)

Clare Leschin-Hoar's stories on seafood and food politics have appeared in Scientific American, Eating Well and elsewhere.

Millions of California chinook salmon won’t be meandering their way downstream this spring because California’s extreme drought has meant important waterways, such as the Sacramento River, are running too low to ensure that the young fish can make their way to the ocean. But that doesn't mean the multibillion-dollar industry is drying up too.

Instead, nearly 30 million of the fish will most likely be hitching a ride to the Pacific Ocean via 18-wheeler.

State and federal officials announced their contingency plan earlier this week, which involves loading millions of hatchery-born salmon onto climate-controlled tanker trucks for a three-hour drive to San Pablo Bay, where they’ll then be placed in net pens. After that, they'll be released for sport and commercial fishermen—who will eventually sell to stores and restaurants.

“We give them time to get reoriented, and then those pens are towed out to deeper water, where the fish are let go,” says Bob Clarke, fisheries program supervisor at the U.S. Fish and Wildlife Service, whose agency runs the Coleman National Fish Hatchery—the largest salmon hatchery in California, raising nearly 12 million salmon a year. 

California operates four hatcheries that produce salmon in the Sacramento system and two facilities farther north—several facilities are laying similar plans to the trucking course at Coleman.

Under normal circumstances, Coleman National Fish Hatchery would time salmon releases with spring rain events in April and May. The last time the hatchery had to truck smolts to the ocean was in 1991 and 1992.

“But this year is extraordinarily bad,” says Clarke.

John McManus, executive director of the Golden Gate Salmon Association, has been pressing for the trucking plan for months, saying low water levels and warmer river conditions would have likely wiped out the hatchery fish had they been released into the river.

“What this means is we’ll likely have a much better salmon fishing season in 2016, when these fish reach adulthood, than we would have otherwise gotten,” says McManus.

Low water isn’t the only threat migrating salmon face this year. Drought conditions prompted the state to divert water through man-made canals to pumps (that can suck migrating salmon into them) and reroute the water for farming purposes. Traditionally those water channels are closed during spring migration months so salmon can complete their passage safely. This year the channels have remained open to help dilute higher salt levels caused by the drought.

Low water levels have also prompted worries over wild salmon too. While the majority of salmon returning to the Sacramento Basin are of hatchery origin,and make up the majority of locally caught salmon in California, the state still has some naturally spawned wild fish too, with no one to truck them to the ocean.

Harry Morse, spokesperson for the California Department of Fish and Wildlife, says their survival rates vary greatly, depending on water conditions and food supplies once they make it to the ocean, but says they won't know how the wild salmon have weathered the drought until they return in August. Right now, the forecast for wild salmon is "not favorable," he says.

Water quality near the hatcheries is another area of concern.

"We're looking at the water quality near the hatcheries—that they remain viable. That is a very serious issue here," says Morse. "We have four major salmon hatcheries where the water quality is good. We have 17 inland trout hatcheries with water variations that we're watching very closely."

Even if officials get the salmon safely to the ocean, it won’t ensure they’ll find their way back as adults. Without migrating downstream on their own, the fish will be missing important imprinting cues. Imprinting is like a memory of a scent that helps salmon identify which river to return to when it’s ready to spawn.

“If you take them and drive them, that process is interrupted,” says Clarke. “They won’t have the same ability to get back to their native stream. They get lost. We call it straying. They’ll stray to different parts of the Central Valley, which isn’t a good thing.”

Wildlife officials want to avoid a scenario where not enough salmon will return to the hatchery in the future, and there are worries that the hatchery fish will mix with wild salmon.

“We have the hatcheries in the first place to mitigate the loss of habitat when the dams went in and blocked migration. Thousands of fish lost their spawning habitat,” says Clarke. “The goal at Coleman National Fish Hatchery is to have adults return, all while minimizing impact of natural-run salmon in the Central Valley.”

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