Chinook salmon, a keystone species in the Pacific Northwest, hold together the ecosystem, feeding orcas and other wildlife and returning crucial nutrients like nitrogen and phosphorous to the Columbia River basin when they decompose.
Many salmon from the Columbia River and its tributaries are endangered or threatened, including the native Tule Fall Chinook salmon reared at the Spring Creek National Fish Hatchery just west of White Salmon along the Columbia.
Hatchery programs are meant to support the wild salmon population, but it turns out that hatchery fish don’t fare as well as their wild counterparts.
It’s a problem that pinged the radar of Rikeem Sholes, scientist with the US Fish and Wildlife Service and doctoral student in neuroscientist Allison Coffin’s lab at Washington State University Vancouver.
“We’re seeing some abnormalities in the mechanosensory system in hatchery-raised fish,” Sholes says. “We know that’s leading to hearing loss and might also be energetically taxing for them because that system helps them navigate.”
The mechanosensory system comprises the salmon’s inner ear as well as its lateral line, a network of external sensory cells that runs around the head and down the length of the fish’s body. These cells—called hair cells or neuromasts when considered along with their support cells—sense vibrations and water movement to help fish detect prey and predators and orient themselves in the water. That’s especially important for fish like salmon that must navigate thousands of miles to reach the ocean and then return home to spawn.
Sholes says neuromast damage may result from noise exposure in the hatchery. In addition to the occupational noise of a working hatchery—which Sholes describes as thunderous like a waterfall—a railway system and major highway flank Spring Creek. And, unlike wild salmon that can simply move to quieter waters, hatchery fish are stuck in that industrial setting until their release.
Spring Creek provided Sholes 12,000 Chinook salmon, which he split into three groups: one reared under normal hatchery conditions, one raised in soundproofed containers, and one exposed to a constant 150 decibels of white noise.
Sholes notes that “150 decibels sounds very loud for air, but it’s not atypical of what they would be exposed to underwater” in a hatchery.
For context, most emergency sirens come in right at 120 decibels while the blistering bang of fireworks is a solid 150 decibels.
The early data suggest the salmon exposed to white noise may have fared the worst when it comes to reduced neuromasts along their trunks, but survival data will remain a mystery for some time. Sholes tagged the fish before sending them off on their perilous journey out to sea.
As they pass dams and hatcheries outfitted with antenna arrays, the pill-shaped trackers nestled in the salmons’ bellies will ping, letting Sholes know where they are and what direction they’re heading. The salmon are expected to return to Spring Creek sometime between 2025 and 2027.
That return trip is notoriously brutal; while they travel, the salmon’s bodies will begin to decay as they resorb minerals and nutrients to fuel the journey. Does protecting the fish’s mechanosensory system at the start of their lives provide a boost that makes them more likely to make it back home?
Sholes will be there to find out.
Melissa John Mayer is a science educator and writer for WSU’s Ask Dr. Universe program.
Have you heard? (Summer 2023)