In the wake of floods, what’s next for salmon in the Pacific Northwest?

Morse is just one of thousands of people across western Washington and British Columbia who experienced severe flooding in mid-November. A potent atmospheric river storm — a long, narrow corridor of tropical water vapor that, when forced upward by obstacles like mountain ranges, condenses and sheds moisture — dumped massive amounts of rainfall, sometimes up to half an inch an hour, on the region. Bellingham, Washington, received more rain between Nov. 14 and 15 than it usually does in the entire month. Rivers like the Skagit and Nooksack spilled over their banks, and salmon, like the ones Morse saw on his driveway, were washed out of their streams. Mudslides wiped out roadways, and three out of every four homes in Sumas, Washington, were damaged by floodwaters. At least five people died.

As communities turn to cleanup efforts and brace themselves for yet more rain, experts say that the flooding could have both positive and negative ecological impacts on salmon. Salmon, a keystone species in the Pacific Northwest, are an important food source for 138 other species, including orcas. They’re also an essential component of regional tribes’ culture and sustenance, and they support an estimated 16,000 commercial and recreational fishing jobs.

Salmon already face numerous threats, including warmer waters caused by climate change, habitat loss, blocked migration routes and toxic stormwater runoff. Five species of salmon call Washington home: Sockeye, coho and chinook are locally endangered, while chum and pink are not. A 2020 report concluded that Washington’s salmon “remain on the brink of extinction.” It doesn’t help that this year’s already been rough for fish: A record-breaking heat wave in June caused widespread ecological fallout, and in September, warm water, low flows and bacteria killed thousands of endangered chinook before they could spawn in the South Fork Nooksack River. Treva Coe, a fisheries biologist and watershed restoration program manager for the Nooksack Indian Tribe, says the heavy rains could make salmon numbers dip further. “We do know from data on our populations that years with low survival are associated with years with high flows and large floods, so we’re really concerned that this year class survival is going to be low, if not wiped out,” said Coe.  

A few days after Morse saw salmon swimming down his driveway, they became food for eagles and raccoons. Salmon are anadromous, meaning they are born in rivers, spend most of their life in the ocean, and then return to freshwater to spawn before they die. Chinook, pink and sockeye salmon were spawning or had already spawned before the storm, meaning they were most likely the fish Morse saw, washed out of a channel and trapped in shallow water after reproducing. Their time was limited, anyway. But what about their descendants?

Salmon embryos are initially buried under gravel so they don’t float away. “They’re very vulnerable at that stage,” said George Pess, a watershed program manager at the National Oceanic and Atmospheric Administration’s (NOAA) Northwest Fisheries Science Center. “Floods could set the trajectory for this brood year.” Fish in the alevin stage are still growing and cannot move for a month or so, and even once they emerge as fry, they’re only 35 millimeters — a little longer than a quarter coin. Females can lay from 1,000 to 7,000 eggs, but depending how badly floodwaters churned up river bottoms, many of those eggs could have been unearthed from their hiding place, swept into the water column, and ended up as tasty treats for a variety of predators.