Why are salmon dying when they reach saltwater?

A new research program, announced yesterday, will work to untangle the mystery of what is killing young salmon after they leave their natal streams. The program is being coordinated in both Washington state and British Columbia — by Long Live the Kings on the U.S. side and by Pacific Salmon Foundation in Canada. See today’s Kitsap Sun (subscription required).

At high tide, water now covers what had been a farmer’s field after an old farm dike was breached in two places on Monday. Two bridges allow continued access along a trail across the dike. Photo by Steve Zugschwerdt
At high tide, water now covers what had been a farmer’s field for decades on the Union River estuary near Belfair. On Monday, an old farm dike was breached in two places. Estuaries are considered important for salmon survival. / Photo by Steve Zugschwerdt

I have conducted hundreds of interviews about salmon through the years. Biologists can usually explain what makes a good salmon stream: clean water, sufficient gravel, vegetation to provide food, woody debris to provide protection and so on.

What they cannot explain very well is what young salmon need to survive in saltwater. Is it clean water, as in freshwater environments? Is it a particular kind of plankton for food, or maybe natural shorelines to provide protection during migration? Is the increased marine mortality of salmon the result of disease or predators? All may be factors, but which ones really count?

When asked to explain why salmon runs are coming in larger or smaller than predicted, salmon managers typically fall back to two words: “ocean conditions.” Conditions may be good or bad in a given year, but what makes good or bad conditions cannot be answered very well.

Biologists who predict salmon runs talk about the “black box” that salmon swim into when they leave the streams and swim back out of when they return. It’s a way of saying that the computer models used to predict salmon runs have a blind spot when it comes to the deep, dark ocean — which we now believe includes the estuary at the edge of the stream, where the salmon change from being a freshwater fish to being a saltwater fish.

“What is currently recognized as a black box appears to be a black hole for salmon recovery,” Jacques White, executive director of Long Live the Kings, told me yesterday in an interview. “If we don’t know what is going on, we can’t make decisions for salmon recovery. It makes it difficult to manage the stocks coming back.”

That’s where the cross-border research program comes in, and it’s no wonder that salmon biologists are excited about the prospect of breaking into the black box. It won’t be easy to track the tiny fish after they leave the streams or to figure out where things are going wrong, but new technology will help. The project is proposed for $10 million in the U.S., with an equal amount in Canada.

Review the Long Live the Kings website for other information about the Salish Sea Marine Survival Project. To go deeper into the ideas behind the project, download the proceedings, notes and other information from November’s Salish Sea Workshop Series.

Meanwhile, efforts to improve estuarine and shoreline conditions will continue, using natural conditions as a guide. On Monday, I covered the final step in the Union River estuary restoration, which involved breaching an old farm dike in two places. I watched as the waters of Hood Canal, held back for a century, began to reclaim 32 acres of saltwater march. Check out the story and video in the Kitsap Sun (subscription required).

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2 thoughts on “Why are salmon dying when they reach saltwater?

  1. I would love to see the area near Allyn, called North Bay in Case Inlet in your studies. It is obvious to any casual observer that the ecosystem has been nearly destroyed by careless planting and harvesting of goeducks for sale to Japan at extremely high profits. The Taylor Shellfish Company has convinced the State of Washington to lease them tide lands for this purpose. This company uprooted nearly all sea weed species by using power hoses to harvest the existing goeducks. Along with the seaweed went the ecosystem needed for the survival of numerous fish and shellfish species. They then planted goeducks seed in tubes made of PVC pipe. The shavings from the PVC are ingested by marine life, causing more devastation. Over time the PVC continues to dissolve in the salt water. To make matters worse, the PVC tubes are covered by netting to insure that the immature goeducks do not float from the PVC tubes in which they are planted. This netting acts like a gill net, catching and killing any fish which used to used to be called bottom fish such as cod, sole, etc. Durung low tides other species such as birds, including Bald Eagles become entangled in the webs struggling until they die. Needless to say, the salmon returning to Coulter Creek, die when attempting to reach salt water. The State of Washington has so far considered this an acceptable loss. A few years ago they simply gave up all,efforts and closed the Coulter Creek,Hatchery.

    We have a new governor and new groups showing concern for the survival of Puget Sound. Can you direct us to,those who can help,us save the ecosystem in North Bay?

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