How fast can salmon swim?

Salmon are some of nature’s best athletes, boasting the ability to swim thousands of kilometres upstream passing roaring rapids, swirling eddies, and snarling predators.

But one of the simplest, and most-important questions about their physical abilities remains largely unanswered. Because even as scientists, non-profits, communities ,and organizations work to improve salmon populations in British Columbia, it’s still unclear just how fast a salmon can swim.

Speed is not a trivial matter. Knowing a salmon’s top speed would allow conservationists to build better fishways, and could help scientists when landslides, flooding and other emergencies threaten the species. But as researcher Krista Kraskura recently found, even the use of fish “raceways” and high-tech tags have yet to lead to a satisfying answer to the question: just how fast can a salmon go?

A non-trivial question

Every kid knows the fastest land animal is the cheetah.

There are entire nursery rhymes constructed around the common knowledge of which animals go fast and which go slow. But while a little boy or girl might be able to rattle off the top speed of a peregrine falcon, even a salmon-obsessed scientist with a PhD like Krista can’t comfortably answer how fast a salmon can swim.

And that’s a problem.

In 2019, a landslide at Big Bar on the Fraser River, just north of Lillooet, created a five-metre waterfall. The waterfall blocked the spawning runs of salmon that would seek to lay eggs in northern BC, and sparked a large, multi-government response to restore the ability of salmon to get past the slide. “Salmon cannons” were installed as a temporary measure, while crews blasted away rocks to reduce the height of the rapids and the speed of the water. A fishway was also created.

The event—and the response—revealed to Kraskura, her colleagues, conservationists, and government officials the importance of knowing exactly how fast fish could swim.

Speed bursts, she said, are “an essential part of their migration.” Salmon use their bursting ability to get through rapids like those in the Fraser Canyon, at Big Bar, and elsewhere along their journey.

“It was a very immediate conservation concern,” she said. “So that was where the work came in: to be like ‘OK, what do we really know about sprinting speed?’”

So Kraskura, a researcher at the University of California, started collecting and analyzing all scientists’ attempts to answer the question in what would become a paper published this August in the Canadian Journal of Fisheries and Aquatic Sciences. (The paper was produced in collaboration with Chilliwack-area Department of Fisheries and Oceans biologist David Patterson and Kraskura’s University of California colleague Erika Eliason.)

As Kaskura researched the subject, she became even more convinced of the practical relevance of knowing just how fast a fish can swim when pushed to its limit. Such information could impact how rivers are managed, how scientists assess the potential impact of landslides and floods, and how conservationists and governments design fish-friendly routes and infrastructure around human obstacles.

A salmon’s top speed is also important because bursts of speed aren’t good for spawning salmon, which are typically a slow-and-steady species. The majority of the time, the fish swim at a steady pace of about 50 centimetres per second—a little less than 2km/h. If they don’t have to go fast they won’t, especially during their spawning migration, when they don’t eat and must judiciously conserve all the energy reserves they have accumulated in the ocean.

So while they may be capable of intense bursts of speed, that exertion is draining and dangerous. After such an effort, a salmon will have to pause and recharge. Some may not be able to do so.

“If they run out, they run out,” Kraskura said. “They might be able to swim past a certain location, but they might not be able to recover from that.”

Knowing more about a salmon’s top speed can help scientists understand how high-water conditions may impact the fish’s ability to make the journey upriver and reproduce.

But as Kraskura and her colleagues learned, despite a massive amount of research into salmon and their swimming ability, scientists are still struggling to settle on a top speed for salmon

Salmon speedways

It’s relatively easy to train a radar gun on a cheetah sprinting across the savannah. It’s infinitely more difficult to clock a fish that specifically avoids concentrated bursts of speed and which, when they do sprint, does so within water that is moving in the opposite direction.

Most research on salmon swim speeds has focused on measuring how fast the fish can swim over a sustained length of time, rather than in short bursts used to overcome certain obstacles. Those studies have generally employed the use of salmon “raceways,” that are half fish drag strip, and half treadmill.

Many raceways are large rectangular or circular containers. Water is propelled in one direction while fish swim the other way to hold their place in the man-made “river.” The raceways are commonly used by salmon farms to recreate a river’s current and allow juvenile salmon to “swim” in place as they mature. Scientists can also use them to measure the physical abilities of the salmon they are researching, increasing the speed of the water until the fish are not able to keep up and begin falling behind.

But Kraskura says the setup isn’t ideal for testing the brief but massive bursts in speed that salmon are capable of performing.

As Kraskura and her colleagues write: “swim performance has been measured using swim flumes, but evidently adult salmon can swim faster in the wild than this set-up can capture.”

Salmon can swim at peak speeds far above their normal sustained speed, but they can only do so for a very short period, presenting challenges when it comes to deploying a raceway.

There is some hope. Kraskura’s paper points out that raceway flumes have been created to specifically measure top speed among other fish. But so far, nobody has published research about their use to clock salmon.

Other speed measurement techniques are being tested. Some use lasers and cameras to try to measure a salmon’s speed within very large fish raceways. Scientists are also analyzing the physiology of sprinting salmon, trying to correlate the frequency of a fish’s tail’s wag to its speed.

Some of the most-promising studies have used tags inserted into the fish during real-life migrations. But those have their own complicating factors. Because salmon are swimming opposite to the flow of water, their maximum speed can’t just be measured by how quickly it crosses a certain stretch of water. So the tags must be calibrated in labs in order to actually produce useful data. It’s a little like having to figure out the top running speed of a sprinter if you could only measure them while running against hurricane-force winds. Tags can also impact a fish’s ability to swim, according to one study.

All of which is a long way to explain why, despite the importance of knowing how fast one of BC’s cornerstone animals can swim, we still aren’t quite sure just how fast a salmon can really go.

So how fast can salmon swim?

That’s not to say scientists are completely in the dark. They may lack sufficient top-speed data to know how fast healthy salmon—as a population—can go when pushed to the limit, but they do know how fast at least a few salmon have swam. And it’s pretty darn fast.

One study clocked a fish at about eight metres per second. That’s about 29 km/h, a speed approaching that of a world class 100-metre sprinter. That turn of pace is around four times faster than the top speed salmon can typically muster over a longer, more-sustained duration.

But much more data is needed to answer all the questions that scientists and conservationists have. Because a few isolated studies and speed recordings won’t do when it comes to learning about an entire species.

Imagine aliens descend on earth and start trying to measure the top speed of humans. Even with alien-grade technology, the conclusions they draw would be influenced by the humans they measure. They would likely come to much different findings depending on whether they chose specimens of an international track meet or a low-grade fast-food restaurant. The speed of their test subjects would also likely change depending on whether their humans are asked to run in the freezing cold, a 20C degree day, or in the blazing heat.

So to come to a solid understanding of a species’ physical capabilities, researchers—whether they be aliens or salmon researchers—need to test as many specimens as possible in as many different conditions as possible.

Which is why, although Kraskura can cite a few studies that have clocked salmon at certain peak speeds, we don’t quite know just how fast those fish are compared to all the other salmon out there.

The next step

Null findings—the discovery of an absence of something—are important in science, but rarely rewarded. An academic who discovers something can expect more praise, professional advancement, and institutional funding than an academic who debunks a study or finds an absence of proof.

Kraskura, though, is fine with the ambiguous outcome of her research, because what she found was perhaps even more exciting than an answer: a mystery with increasingly obvious real-life stakes. And a path to better answer that mystery.

The data Kraskura and her colleagues collected represent the most we know on salmon speed. And that collected data is already informing both academic research and on-the-ground activity. During the research, which coincided with her work as a PhD student under Eliason, Kraskura fielded inquiries about salmon speed from those involved in the design of salmon fishways.

“That was really inspiring,” she said.

So although the estimates collected in the paper might be relatively broad, they can still inform decisions made today by those building new fish-friendly infrastructure. And as a whole, the paper can lay the groundwork for a new era of speed study research—one that may finally reveal just how fast BC’s most important fish can swim.

“There’s a lot of work to be done. But in a very good way.”

Correction: This story incorrectly said Erika Eliason was American. Although she works atin the US, Eliason is Canadian.