Fish Cannon

This is 99% Invisible, I’m Roman Mars.

RM: During the Cold War, a so-called “iron curtain” separated Eastern & Western Europe. Communism from Capitalism. The Soviet Union from everyone else. In some places, it was an actual wall, like in Berlin. And in other places, it was just a barbed wire fence. This border was long, stretching from Northern Finland, through Central Europe. It covered twelve and a half thousand kilometers or almost eight thousand miles. And all along this eight thousand mile border, there was a no man’s land: a couple hundred yards across, where there was almost no human activity.

EF: When the cold war ended, and the walls and fences came down, people noticed something interesting.

RM: That’s reporter Emmett Fitzgerald.

EF: This neglected strip of land had become a productive ecosystem. With forests, and fields, it was a haven. Particularly for migratory birds.

RM: Soon after the Berlin wall fell, conservationists from East and West came together to protect this accidental refuge for birds and animals.

EF: Because the no man’s land was so long, they realized that it could link habitats throughout central Europe. Today, the so-called “European Greenbelt” traces the path of the old Iron Curtain. It connects national parks, and nature preserves, and helps animals move around in a landscape dominated by humans. It’s what’s known as a wildlife corridor.

LM: Wildlife corridors can link two extremely large habitats like two national parks or two national forests, or a national forest and a national park. Say, across a very large freeway. Or it can link relatively small fragments of habitats within very developed metropolitan areas.

EF: That’s Louise Mozingo. Chair of the Department of Landscape Architecture and Environmental Planning, at the University of California, Berkeley. And she says that a wildlife corridor doesn’t have to be a massive greenway through Europe.

LM: It could be something as simple as a concrete pipe, or a small, kind of vegetated ditch under a freeway…

EF: Wildlife corridors might be the most critical in urban areas. Because sprawling cities and highways have fragmented a lot of wildlife habitat. And have forced animals into isolated pockets which is a problem, because animals need to move around to find different food sources, and mates.

RM: In Southern California, an abandoned highway underpass began to link two important pieces of habitat in an otherwise industrial area.

LM: And what they found, is that both of these habitat zones actually were able to support much larger populations than expected because this relatively small, concrete underpass was able to connect the two habitat ranges. And so you had even very large predator species like mountain lions being able to be supported by these fragments of habitat in a very urbanized situation.

EF: Today, the abandoned underpass is purposefully protected, And maintained as a wildlife corridor.

RM: But wildlife corridors don’t have to technically be corridors. They can be any piece of design that facilitates the safe passage of animals through the human-built environment. From one piece of habitat to another.

EF: And they’re not always a product of accident and neglect. Sometimes they’re very intentional and carefully designed.

RM: One of the oldest examples of humans designing a passageway for animals is the fish ladder. Which helps migratory species of salmon and steelhead trout get over dams that block their annual migrations upriver to spawn.

EF: First patented by a Canadian lumber mill owner in 1837, the standard fish ladder is a series of terrace pools with just enough space between them, to allow a fish to leap from one pool to the next, slowly climbing the ladder to the other side of the dam. The design takes advantage of salmon’s natural ability to swim upstream; through rapids, and over small waterfalls.

RM: So a quick lesson in salmon migration: salmon babies hatch in the upper reaches of a river, and immediately start making their way down the river to the ocean. They hang out at sea for a few years, and then, when it’s time to mate, miraculously swim their way back up the exact same river to lay their eggs; using magnetic fields and smell to navigate.

EF: But in the early 20th Century, companies started building giant, hydroelectric dams on almost every major river in the United States. And they were way too big for a salmon to jump over. And so, at some of these dams, engineers installed fish ladders, to help the salmon out.

TD: And fish ladders have worked well over the years. Part of the problem with fish ladders is they tend to be very expensive to build.

EF: That’s Todd Deligan.

TD: My name is Todd Deligan, I am the Vice President of Business Development with Woosh Innovations.
RM: You’ll understand where the name “Woosh” comes from in a second.

TD: Today there are about eighty to eighty-eight thousand barriers in the country that have you know, an elevation of 5 feet or more.

EF: Eighty-eight thousand dams that fish have to get around.

TD: It’s a little hard to tell how many actual fish passage installations are at these barriers, all around the country. But it is somewhere between 10 and 15 percent, we estimate. There a lot of places where a lot of fish aren’t getting anywhere, at all, because of the barriers that exist.

RM: And that’s where Todd’s company, Woosh comes in.

(newscaster) Fired into the sky, these salmon are becoming flying fish…

(newscaster) If you didn’t think fish could fly, think again. I introduce you to the Woosh Fish Cannon. Take a look…

EF: You heard them right, the salmon cannon.

RM: The salmon cannon actually started out as an apple cannon. The founder of the company, Vince Bryant, owns apple orchards along the Columbia River in Eastern Washington. And he noticed that the pickers were spending a lot of time carrying fruit from the trees to storage bins in the center of the orchard.

EF: It was inefficient. So Vince and Todd built this soft tube, kind of like a firehose. And inside the tube, they generated a pressure differential, capable of sucking an apple hundreds of feet, and depositing it gently in a storage bin.

RM: So they have this effective device for apple picking. And pretty soon they’re thinking bigger. In the Pacific Northwest, nothing is bigger than salmon.

EF: The Columbia was once one of the world’s great salmon rivers. But today, fourteen dams block the fishes path home. And the Columbia salmon migration is a thing of the past.

TD: We were um, working in the apple orchards in Eastern Washington, right along the Columbia River.

RM: Vince and Todd could actually see two of Columbia’s dams from the orchard.

TD: We sort of looked at each other and said, “Well, what if you could put a salmon in the tube?”

EF: The idea seemed ridiculous at first, but they couldn’t let it go.

RM: So Vince and Todd head back home, to their shop.

TD: We set up a fruit tube in our shop. It was about 25 feet long or so, and put a dead salmon in it. A small dead salmon and a couple of dead trout.

RM: So they put the fish in the tube and woosh! It popped out on the other side.

TD: And then we went out and bought some live Tilapia to see if transport through our old agriculture tube would cause any effects. You know, are there going to be any damages to the fish? Are the fish gonna live? And uh, that tube was about 20-25 feet long also. We put the live tilapia in and they went flying into a tank of water and started swimming around immediately and had no issues. Ah, you know, we just high fived, ourselves. (laughs) It was great.

EF: So from there they set about retrofitting their apple tube to transport fish. And a few months later, the salmon cannon was born. But okay, it’s not really a cannon…

TD: They aren’t being blasted out in any way, shape, or form.

EF: The salmon cannon, by Woosh Innovations, works like this: First, they have to get the fish to swim into the tube. Salmon evolved to swim upriver; past rapids, and over waterfalls. And they’re attracted to flow. So the company built a false rapid, in front of the tube.

TD: in essence, a very small waterfall with you know, sufficient flow to get the salmon to a particular place along the barrier itself. They are attracted to the flow; up and over they come over this sort of first step, uh, and literally they will just be directly guided into our tube itself.

EF: Once inside the tube, a pressure differential moves the fish forward.

TD: So that fish then accelerates through the rest of that tube whether it be 50 feet or 300 feet. They’re traveling somewhere between 15 and 22 feet a second.

EF: Inside the tube, it’s soft and slippery with almost no friction.

TD: They are in, in essence, a slippy slide for fish. You can see some videos where the fish are almost actually swimming. They’re doing their natural um, swimming action through the tube itself.

EF: And when they reach the top of the dam…

TD: Then they find themselves right back in the river itself. So they can continue their journey, on the other side of the dam with a barrier.

RM: The salmon cannon is still pretty new. Right now it’s being used on the Washougal River in Washington state. And they’re trying to sell the system to fish and wildlife agencies throughout the region. A lot of scientists who have tested the system seem excited. Particularly because it seems to cause such little stress for the fish.

EF: But not everyone who cares about salmon is so gung-ho.

DM: It seems like if you need to resort to a cannon, to get a fish moving through a river system, then maybe there’s something more fundamentally wrong with the infrastructure system.

EF: This is David Montgomery.

DM: I’m a professor of Geomorphology at the University of Washington. And I’m the author of the book, The King of Fish: The Thousand Year Run of Salmon.

EF: And David’s point is, “Look, the fish cannon may very well be able to get an adult salmon over a dam safely, and cheaply, but that’s just treating a symptom of a deeper problem.”
In some cases, rivers with lots of dams aren’t even really rivers anymore. Just look at the Columbia River; the one right by Vince & Todd’s apple orchard.

TD: It’s a series of lakes. I mean, you can go waterskiing on it.

RM: The dams on the Columbia have turned what was once a mighty torrent, into a chain of stagnant reservoirs. And that creates problems that things like fish ladders and salmon canons can’t fix.

EF: When salmon eggs hatch, the babies need to get back down the river, to the ocean.

DM: The juvenile salmon of the Columbia River used to basically surf down the river. They just got out into the current, oriented themselves, and the river took them to the sea. Now, what happens if the river is no longer a river, just a series of lakes? They have to swim all the way down. They didn’t evolve to do that.

EF: This has been a problem for a long time. One that no one has really solved it yet.

RM: Some babies are making it down, but not enough.

EF: On some rivers, people have resorted to transporting baby salmon downstream with boats and trucks.

RM: David’s not trying to single out the salmon cannon. There’s been a whole host of technologies that people have experimented with to help fish get around dams.

DM: But really the underlying problem is that you’ve ecologically turned a mighty river into a series of lakes.

RM: The Washington state government spends millions of dollars every year on fish ladders, and other efforts to get fish around dams but the numbers are still way down.

DM: Around the Puget Sound, where I live, around Seattle, we’re estimated to be down to about 10 percent of the salmon that we had historically. Throughout the region, it’s somewhere like 5 or 8 percent, and the Columbia River I think it’s down to 2 percent. You know, it varies.

RM: Salmon decline is complicated. It has to do with several factors, such as over-fishing and Habitat destruction.

DM: And I think that that’s a characteristic of a lot of environmental systems. They’re actually more complex than we realize.

EF: And the worry is that many of these technological solutions to environmental problems, only solve a piece of the problem without dealing with the overall health of the ecosystem. You might be able to get the fish up the river, but the river itself is still broken.

RM: With that in mind, people have recently started calling on the government to remove old dams and return entire river systems to their free flowing state.

DM: The idea that you could actually take a major dam 20 years ago was crazy talk. I mean, that was just not something that you would sort of, that people would talk about as a serious political or social possibility.

EF: But now, it’s happening. After years of protest by indigenous people, and conservation groups, dams have come down in the Sandy River in Oregon, and the Elwha River in Washington state; and the salmon have begun to come back.

RM: We’re not gonna get rid of every damn dam in the country, but a lot of them are reaching the end of their structural lifetimes. And some are just not profitable anymore. And in those cases, David wants us to look at each one on a case by case basis and ask,

DM: Well what about this one? Does this one still make sense?

TD: Todd Deligan of Whoosh supports taking out old, unprofitable dams. But a concern for anti-dam activists is that technologies like the salmon cannon could slow down these efforts, or even enable more dams to be built because companies can say, “Well don’t worry about the salmon migration, people have designed solutions to that problem.” And that’s a worry with wildlife corridors more generally.

LM: Wildlife corridors cannot be a substitution for preservation of key habitat areas.

EF: That’s Louise Mozingo again from UC Berkeley.

LM: The reconnection of fragmented landscapes should not be an excuse to destroy existing really high-quality habitats. We have too few of them, and we need to preserve the ones that are functioning really well, that are supporting large and diverse wildlife populations.

EF: Corridors only really make sense she says, in places where habitats have already been fragmented.

LM: And now you can knit them back together in ways that support, if not a robust population, an adequate population for the species to survive.

EF: And in those situations, where humans have already had a huge impact on the landscape, design for the benefit of non-humans, could be the key to keeping wildlife around.

RM: We spent most of the 20th Century carving up, and dividing the landscape with impassible objects made of asphalt and concrete. But if you zoom in, you can see the effort to stitch together habitats with the tiniest of threads that can make all the difference. A crab ladder here, a salamander tunnel there. And that’s great, but if we’re honest, we can’t fix every problem we created by building something new. For a species like salmon to survive in the modern world, it’s going to take a patchwork approach, of addition and subtraction. Sometimes the best thing for wildlife is for us to just do our best to stay out of the way.

Comments (14)


  1. cochese

    Holy smokes, one of the narrators talks out of the back of his throat the whole time… its super annoying.

    1. Matthew

      I thought that the whole concept of fish ladders were more or less an abysmal failure?

      There’s a really great documentary (available on netflix) called DamNation that talks about the horrid track record and devastating environmental impact of dams, and how much of what they promised was never really delivered upon, or that their electrical generation was not necessary. Highly recommend checking it out!

  2. Kevin

    I am all for removing unnecessary dams and increasing and improving Salmon habitat however, the assertion that the Columbia is a series of lakes is incorrect. I am on the Columbia every week and I can tell you that this claim by the ‘no dams’ advocate is pure hyperbole. Come down and enjoy the Columbia River and see for yourself.

  3. Alison Oakleigh

    Hi guys,

    I’m a long-time listener and lover of the show. You guys and the whole radiotopia network have me evangelically hooked on podcasts. Thanks. Packing the dishwasher and commuting haven’t been the same since I found you, and for this I’m eternally grateful.

    Anyway – in this episode – great as always – Roman says (at about 3:26) “one of the oldest examples of humans designing a passageway for animals is the fish ladder…” – OK, cool. BUT I’ve completely got to tell you all about this INCREDIBLE design that the Australian Aboriginal people did 8,000 years ago, building passageways for eels, to farm them.
    See here:

    And do anything you possibly can to watch episode 4 of the documentary series “First Footprints” because it will blow your mind – which is honestly not something I would ever have imagined I’d say about eel farming, really.

    Ooo, ooo, and episode 3 of First Footprints which talks about the “Tasmanian Toolkit” 10,0000 years ago being the smallest of the Aboriginal nations, which was not because the other tools had not yet been developed, rather because the other tools had been discarded. An example of design development simplifying the toolkit instead of complicating it over time, suggesting a greater focus on social and cultural development. (Reminds me of your stone-age flint tool episode)…

    OK. Thanks, keep up the good work.
    Canberra, Australia

    1. Mike Gonzales

      I came to the website myself to ask this very same question

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