Salmon-counting could be a breeze as environmental DNA technology advances

Researchers found environmental DNA can be detected in the air above salmon streams, opening new possibilities for non-invasive monitoring

Environmental DNA (eDNA) has become an accepted, non-invasive way to detect the presence or absence of different species in bodies of water. Testing water samples for pieces of DNA that fish and other organisms shed while in the water has been particularly helpful in measuring salmon runs, where assessing a sample of water can give researchers, aquaculture and government partners an idea of how much salmon is actually there.

But water-based sampling may soon be old hat – or only one way to track eDNA. That’s because a new study from the University of Washington proves that researchers might not even need to get into the water to detect what fish and other organisms might be living in it. It shows that eDNA can also be detected in the air via a collection system that doesn’t require any power sources.

“It’s very hard for fish to hide their DNA,” said Ryan Kelly, professor of marine and science affairs at the University of Washington and director of the eDNA Collaborative. Turns out that’s true for the water above where they’re swimming too.

Environmental DNA, or eDNA, itself is not exactly new. It was introduced to the scientific world in 1987 by then-EPA scientist Tamar Barkay, who wanted a better idea of what was living in different kinds of Florida mud. It has since become an inexpensive but powerful surveillance tool, even if it took some convincing to take hold.

Jamie Glasgow, director of science, research and ecology at the Wild Fish Conservancy, said their organization began using eDNA in 2015.

“When I was trying to explain eDNA to people who had never heard of it, there was a lot of skepticism. It sounds like science fiction,” he said.

The organization put it into practice along with more conventional surveillance methods like visual observation, dip net or electrical current, and over the last 11 years found that eDNA produced reliable results. It was also picking up on things that other surveillance methods did not.

“It’s a lot more effective at identifying rare and cryptid species, like fish you might miss if you were doing a more conventional survey,” he said.

For example, the organization has used eDNA to map the distribution and range of Olympic mudminnow, a small cryptid that only exists in the western lowlands of Washington state, usually sticking to mud in areas that are too warm or have too little oxygen for salmon or trout to survive. They’ve also found salmonids much further upstream than they had expected otherwise and been able to better understand the distribution of freshwater mussels.

“It’s an exciting advancement in our field,” he said.

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There’s a lot to see when observing a salmon run, including fish jumping out of the water. That led Aden Yincheong Ip, research scientist of marine and environmental affairs at the University of Washington, to wonder if those fish would be leaving their genetic material in the air too.

In a recent study published in Scientific Reports, he and a University of Washington research team, including Kelly, detailed how they found that eDNA can move between air and water. They put filters 10 to 12 feet above a spawning stream, and left them out for 24 hours over six days between August and October. In a lab analysis, they specifically looked for Coho salmon-specific DNA. They found that air eDNA fluctuated along with visual counties reported by the hatchery, even if the actual levels of eDNA tested 25,000 times less concentration than eDNA found in the water.

While the system detects DNA at much lower rates than water samples, air eDNA systems can be used in places where power is not available because it doesn’t require any for collection. The system can also be put above freshwater sources where researchers may not easily be able to collect samples from the water itself.

It’s about as low-tech a system as you can get, said Kelly: “You could do it anywhere. You could do it off grid in a forest, or wherever else. It opens up a level of feasibility when you don’t have to haul equipment around with you.”

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For industry, air eDNA is a new potential line of the growing use of eDNA.

“It’s showing that terrestrial things can be found in water samples and aquatic things can be found in the air,” said Elizabeth Andruszkiewicz Allan, general manager at Wilderlab USA (she is also a former employee and co-author on the University of Washington paper; and Kelly works with the company).

Andruszkiewicz Allan sees these results as the “tip of the iceberg,” even if how air eDNA would work in practice needs more refinement and work, especially for industry purposes. Ideally, air eDNA tests would be able to detect multiple species where this paper only focused on one.

But she calls the results a “gee whiz moment of seeing how much potential there is a non-invasive, non-high tech sampling method for routine monitoring.”

Overall, Kelly sees eDNA as “a completely different way of sensing the world around you. Instead of using your eyeballs or using a net to survey and see what’s there, it’s recognizing that we’re totally surrounded by information from the environment.”

Researchers are also looking at detecting eRNA, which degrades faster but can provide epigenetics information, like if the fish were juveniles or adults when in that section of water.

“It gives you a clock of how old the fish is when it’s shedding these cells and put this all together to get a sense of who’s in the environment and what state they’re in,” he said.

Glasgow sees this new air eDNA work as an exciting progression of eDNA technology, which he doesn’t see called science fiction anymore. “We’ve come a really long way.”