Many salmon populations in the Salish Sea are bolstered by releases of juvenile fish that are raised in hatcheries. Juvenile salmon are particularly social creatures, which means many wild salmon may school with (and be influenced by) these hatchery-released fish.

People working with salmon have long suspected that the seaward migration of hatchery fish might inspire wild salmon to migrate out to sea along with them at times when they might not have otherwise made the trek.

Despite this commonly held belief, the hypothesis has never been tested. A SeaDoc-funded study led by Dr. Andrew Berdahl of the University of Washington School of Aquatic and Fishery Sciences will change that.

“We’re basically asking if wild fish feel ‘peer pressure’ from hatchery fish to migrate,” said Dr. Berdahl. “Hatchery production is common throughout the Pacific Northwest, so the findings could improve salmon conservation broadly.”

Various state, Tribal and academic parties are bringing decades of data together from dozens of Washington’s rivers to address this question. It’s an important one considering the dire situation around salmon, and the tribes and Southern Resident Killer Whales that depend on them.

Beyond the direct impact the study could have on salmon recovery in the Salish Sea, the findings could also shed new light on how social systems work more broadly.

Learning how animals make collective decisions (in this case about when to move) may shed new light on (human) social systems and help us to understand how we can promote beneficial, and mitigate detrimental, social contagions.