By Brian Clark Howard
The annual fall run of young salmon from their inland birthplaces in rivers to the sea is one of Nature’s dramatic migrations. But this year, a number of chinook salmon may make that journey by truck.
This week, state and federal wildlife officials in northern California announced that they will ferry hatchery-raised salmon to the ocean in tanker trucks if the Sacramento River system proves to be too dry to support the young fish, thanks to the state’s ongoing drought crisis. Officials fear the river could become too shallow and too warm for the fish to make the arduous journey.
Warm water temperatures can kill salmon outright, and low water can make it hard for them to avoid predators or get around obstacles in the river.
If the plan proceeds, chinook salmon raised at Coleman National Fish Hatchery on Battle Creek, a tributary of the Sacramento River near Red Bluff, could be loaded into trucks and driven nearly three hours to San Pablo Bay near Vallejo. Coleman is the largest salmon hatchery in the state and produces about 12 million fall-run Chinook a year. It had been built to counteract loss of salmon habitat due to construction of Shasta Dam in the 1930s and 40s.
Salmon were trucked successfully during the drought of 1991-1992, and a number have been released that way over the years to protect them from pollution and predation in the rivers. However, there are drawbacks to the approach.
Even though the fish are kept in floating pens in the bay before they are released, they still experience greater shock than if they swam the distance themselves, and that can make them more vulnerable to predation or disease. The salmon may also have a harder time finding the river that takes them back to their birthplace to spawn. They often swim up different rivers, and thereby lead to genetic mixing that may not be desirable.
Scientists think salmon navigate by sensing the Earth’s magnetic fields and by remembering the scents of their home rivers, but a number of experts have warned that hatcheries may disrupt the process, and trucks may make it harder still.
Fall-run chinook from the Sacramento River system are worth millions of dollars to the recreational and commercial fisheries, and represent the largest share of wild-caught salmon off California.
In January, Water Currents reported on chinook salmon stranded in pools on the state’s north coast, thanks to the drought.
A highly prized food fish that is rich in heart-healthy omega-3 fatty acids, chinook salmon (Oncorhynchus tshawytscha) is the largest species of salmon in the Pacific. It is also called king salmon and is native to the north Pacific and rivers of western North America, from California to Alaska. Chinook also spawn in Asian rivers from northern Japan to the Palyavaam River in Siberia. They have been introduced in the Great Lakes, New Zealand, and elsewhere.
Chinook are not listed as endangered as a group, although some local populations are so designated.
Adult chinook may grow up to 58 inches (147 centimeters) long and average average 10 to 50 pounds (4.5 to 22.7 kilograms), but may reach 130 pounds (59 kilograms). They live in the ocean for one to eight years before returning to rivers to spawn.