Already threatened WA salmon could be affected by flooding

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Salmon already face many threats, including warmer waters caused by climate change, habitat loss, blocked migration routes, and toxic stormwater runoff. Five species of salmon have made Washington their home. Sockeye salmon, coho salmon, and chinook salmon are locally threatened, while chum and pink salmon are not. A 2020 report concluded that Washington salmon “remain on the brink of extinction.” It doesn’t help that this year has already been tough for fish: A record-breaking heat wave in June caused widespread ecological fallout, and in September, hot water, low flows and bacteria killed thousands of people. Endangered chinook before they can spawn in the South Fork Nooksack River. Treva Coe, a fisheries biologist and head of the Nooksack Indian tribe’s watershed restoration program, said heavy rains could lower salmon numbers further. “We know from the data on our populations that years with poor survival are associated with years with high flows and large flooding, so we are very concerned that the survival of this age class will be low or even wiped out. “Coe said. .

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

Salmon embryos are initially buried under gravel so that they do not fly away. “They are very vulnerable at this point,” said George Pess, watershed program manager at the Northwest Fisheries Science Center of the National Oceanic and Atmospheric Administration. “Flooding could define the trajectory of this brood year.” Fish in the fry stage are still growing and cannot move for about a month, and even once they emerge as fry, they are only 35 millimeters in size – little more than a quarter of a piece. Females can lay 1,000 to 7,000 eggs, but depending on the severity of the river bottom floods, many of these eggs could have been dug up from their hiding places, carried into the water column and made into tasty treats. for a variety of predators.

Chum salmon swims upstream to spawn in the waters of Pipers Creek at Carkeek Park in Seattle on Wednesday, November 10, 2021 (Grant Hindsley for Crosscut)

“The key is whether the salmon were able to dig their nests deep enough that they weren’t scoured,” said Thomas Quinn, a salmon researcher at the University of Washington. Egg nests, known as nests, can also be crushed by rocks and sand, or suffocated by silt as it settles. “In general, these floods are not good for them,” Quinn said. “I would expect pink salmon to take a hit, and chinook might take a hit.” But as he anticipates the negative impacts, Quinn said, “I don’t think they will be catastrophic.” And species that haven’t spawned yet, like coho and chum, are likely to do well.

A smolt trap on a lower portion of the Nooksack, designed to capture young fish as they migrate out to sea in the spring, will give the Nooksack tribe their first indication of a dwindling population. Similar traps exist on other rivers in the Puget Sound watershed. In four years – when this cohort of salmon matures in the ocean and returns to spawn – the tribe will know if there has been a decline.

George Swanaset Jr., director of the tribe’s natural and cultural resources department, said native people have a duty to protect salmon. The people of Nooksack, he said, have relied on salmon since the beginning of time. “We were fishermen. We lived with these fish, ”Swanaset said. “Without salmon, we no longer exist.

Swanaset and his colleagues fear that the tribe’s habitat restoration projects, including man-made ice jams that create pools where salmon can save energy and find cool water during the summer, have been damaged by flooding. They will have a better idea once the flood waters recede and remote travel is safe.

In this photo taken from a drone, traffic navigates a flooded freeway towards Sumas, Wash. On Monday, November 29, 2021 (AP Photo / Elaine Thompson)

It’s not all bad news: Salmon have adapted to cope with periodic flooding, and landscape remodeling may even create new habitat. High flows are essential to maintaining the complex river systems that salmon need, and flooding is a normal and necessary part of the ecosystem. “While people may be really concerned about these impacts of flooding, it’s important to remember that flooding has been happening for millennia and provides certain benefits to salmon, despite what it might look like. Right now, ”said Bridget Moran, a conservation associate with American Rivers who focuses on Puget Sound and the Columbia Basin.

To the south, atmospheric rivers actually helped salmon back up during years of low flow and high temperatures by providing essential water to watersheds. “We have seen a few different things happening on the Pacific coast, and it has really been a boon for the California salmon,” said Nate Mantua, fisheries and climate researcher at NOAA in Santa Cruz, Calif. .

Unfortunately, human alterations to the landscape – dams on rivers, drying up floodplains for agriculture, narrowing rivers to a single channel – have changed the way floods affect ecosystems and salmon, making flooding more damaging than ‘they wouldn’t naturally be. And experts say climate change is accelerating the timeline of many of the challenges salmon face in the Northwest, from warmer waters to severe flooding. Atmospheric rivers are expected to lengthen, widen, and become wetter in a warmer climate. It is still unclear how this will affect the resilience of the salmon. “We take what they’re more or less evolved from,” Quinn said. “And we’re pushing the boundaries a bit.”

This story originally appeared in High Country News on December 2, 2021.


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