How cannons and snorkelers are helping bring back Seattle's salmon
By Jessie Moravek A few months ago, John Oliver’s “Last Week Tonight” featured the “Salmon Cannon.” The cannon literally shoots live fish over a dam. Oliver, of course, used the salmon cannon to shoot rubber fish at John Stewart (and it was awesome).
The clip certainly got a few chuckles at the office where I was interning—at the Northwest Fisheries Science Center in Seattle, WA, salmon are the name of the game. Seeing them star in pop culture is fun for fisheries scientists, but the salmon cannon also hits on a critical issue: salmon face serious threats across the Pacific Northwest, and it’s up to people to figure out ways to help them.
My internship focused on monitoring salmon populations and habitat. I worked with juvenile (baby) Coho and Chinook salmon in the Cedar River, a mid-sized waterway just outside of Issaquah, WA. The Cedar River is critical habitat for salmon, as well as steelhead trout and bald eagles.
Perhaps more importantly, the river also provides fresh water to 1.4 million people in the city of Seattle. Several dams on the Cedar control the flow of water and are critical to the daily functioning of, well, the entire city. However, the dams can also prevent fish from migrating upstream.
Dams and other river obstacles are a serious problem for salmon because of their unique life cycle. Salmon spend most of their lives in the ocean, but once a year adults swim hundreds of miles up rivers to reproduce. Once they reach their destination, salmon shake eggs and sperm into the water, hope for the best, and die. When the eggs hatch, baby salmon hang out in the river until they’re big enough to swim back out to sea.
Salmon can go really far—some make it from the Pacific ocean all the way to Idaho! But traveling hundreds of miles through a river is dangerous for salmon because they often run into pollution, roads, and dams. If these obstacles prevent salmon from getting up a river, they won’t reproduce, and the population dies out.
That’s where the salmon cannon comes in. As ridiculous as it sounds, the cannon is actually real. It is one of the (less effective) ways fisheries managers try to help salmon move over obstacles in rivers. There are lots of ways people try to move fish past dams—for instance, the Cedar River has a fish ladder, which is basically a hole in the dam that lets salmon jump through.
Ladders and cannons are relatively new inventions, and the Cedar River dam didn’t have either for over a hundred years. That meant salmon couldn’t swim upriver to spawn until 2003, when Seattle installed the fish ladder. Since then, scientists have been monitoring the return of salmon.
My part in all this? Count the fish.
Every summer, scientists from the Northwest Fisheries Science Center survey the number of baby salmon in the Cedar by doing a “head count” of individual fish. You may be wondering how this is logistically possible. You would be right to wonder.
First of all, fish are underwater, and we are not. That’s easy to solve—we used a mask and snorkel. The bigger problem is that the water is COLD. The river is fed by melted snow from the Cascade Mountains, and even on a warm day the water can get down to 45o F. Keeping warm required lots of layers. Over thermal leggings and a t-shirt, I suited up in a thick fleece onesie, a waterproof drysuit, neoprene booties, gloves, and hood, and extra-heavy river boots. Plus the mask and snorkel. I definitely stayed warm, but let’s just say it was a challenge to go to the bathroom.
The more complicated issue is that fish are constantly moving. Several tricks (and several weeks of training) helped me keep track of which fish was which. Often, schools of 20-60 fish hover facing upstream to catch food floating down the river. If you sneak up behind them, it’s pretty easy to get a good count. Once the school scatters, they swim behind you to eat the bugs kicked up by your boots. It takes some major underwater acrobatics to twist around and count a scattered school.
Apart from juvenile salmon, I also kept track of terrestrial (land-based) habitat data. In full drysuit (but sans snorkel), I hiked up and down the riverbank to record information about birds, insects, spiders, and vegetation.
By the end of the summer, my data revealed an interesting pattern. I found that parts of the river with higher densities of salmon had more birds, more spiders, and more insects living on the river banks. That was pretty surprising, because salmon live in the water—who would have guessed they influence land animals as well? It turns out that because salmon spend so much time living in the ocean, they accumulate a lot of nutrients and energy in their bodies. When adults swim upriver to spawn, they carry these nutrients into freshwater environments. This not only helps feed baby salmon, but also supports healthy forest ecosystems.
Why should we care about salmon conservation? Salmon are a critical natural resource in the Pacific Northwest: in 2013, the state of Washington alone pulled in 48.4 million pounds of salmon valued at more than $41.4 million. Salmon fishing and the salmon life cycle also figure prominently into native cultures and local traditions. Keeping salmon safe protects economies, cultures, and traditions—and as I found out this summer, helps keep forests healthy, too.
Salmon conservation in the Pacific Northwest isn’t perfect—there are still a lot of dams without ladders, and fish face a myriad of other problems like pollution and climate change. But the efforts of scientists and local people reflect a desire to find the balance between salmon conservation and human needs. Even if it means loading fish into a cannon.
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