Millions of chinook salmon are produced every year in California’s hatcheries, but many don’t return in the fall once they are released into the wild to grow and spawn. Commercial fishermen and the state Department of Fish and Wildlife have teamed up to find out exactly why and to hopefully strengthen the population of fall-run salmon.

The goal is to find more effective ways to release the fish in the hopes that the salmon will return to the state’s prime breeding grounds. One idea is to transport fish in tanks filled with river water so the fish will have time to get used to its chemical makeup, since salmon return to streams where they are born to spawn. Researchers say the fish are currently unable to get a fix on their native streams, so they get lost on their way back during the spawning season.

“They know how the water tastes and smells from their river of origin,” Colin Purdy, leader of the three-year study, told the Contra Costa Times_._