On May 27, 2021 volunteers with the Millard Piercy Watershed Stewards came upon a startling scene: 65 dead juvenile coho salmon inside a collection box used to temporarily stall and count the fish on their journey to the ocean.
It was a big surprise, said Helmut Novak, the vice president of the stewardship society. The group had installed the smolt fence and counting box at a new location that year, in Courtenay’s Piercy Creek about half a kilometre downstream from the Comox Valley Parkway. They’ve been counting fish in the watershed for years, and no one in the society could recall death counts like the ones then observed in Piercy Creek.
“Never ever before did we have such an occurrence,” Novak said.
Actually, the trouble had started about a week earlier. On May 18, volunteers counted 20 dead coho in the box, which they check and empty daily, moving the collected fish to the water below the fence. On May 19, another 26 coho turned up dead. The next day, an additional 25.
“We didn’t know why,” said Novak. “Initially we thought, well we probably killed it because of our box. I went out and looked upstream of the fence and they’re also dead fish upstream of the fence. So we were obviously relieved that it’s not our box which killed the fish.”
What happened? After investigating the possibilities, the stewardship society has collected evidence that points to the killer: a toxic chemical called 6PPD-quinone that collects in road runoff.
But there’s good news. Unlike many environmental mysteries, this one has a clear culprit and relatively simple solutions.
“This is not a problem which cannot be solved or would be very difficult to be resolved,” said Novak.
Finding the killer
After ruling out the society’s collection equipment, they looked to other suspects.
Was there too much nitrogen in the water, in runoff from nearby cow pastures? No.
In fact, the water in the creek passed all the standard water quality tests. “All the numbers were just perfect,” Novak said.
But there was an important clue. Before the fish started dying, the region was in a period of drought.
“We had many many days almost weeks before the event where we had no rain or insufficient rain,” said Novak.
Then, immediately after significant rainfall, the smolts turned up dead.
You might expect the fish to be thrilled by an influx of water into their drought-stricken creek, but not this time, and not in this place.
Novak searched the internet for clues, and found research from Jennifer McIntyre from Washington State University in Tacoma about the impact of 6PPD-quinone on coho salmon.
6PPD is a chemical used in the manufacturing of tires, which prevents degradation of the rubber when exposed to ultraviolet light. But 6PPD itself degrades over time, reacting with ozone in the air to create 6PPD-quinone.
Novak noticed that the behaviour of the fish exposed to the chemical was the same as the juvenile salmon they found in Piercy Creek. When exposed to 6PPD-quinone, the fish behave strangely and take on erratic movements before death.
SEE ALSO: B.C. stream watchers link ‘unprecedented’ coho salmon kill to tire toxin and drought
“It takes one dose of a certain concentration and it is an irreversible process even when the fish would be brought back into clean fresh water,” Novak said. “They will not be able to recover and recuperate; they will die.”
Millard Piercy Watershed Stewards collected samples of the road runoff from the Comox Valley Parkway, from culverts that ultimately lead to Piercy Creek. Testing found a staggering concentration of 6PPD-quinone, at nearly 600 nanograms per litre.
Recent research suggests that a concentration of just 41 nanograms per litre of 6PPD-quinone over 24 hours is deadly to juvenile coho salmon.
Recognizing the pattern
The relationship between this weather pattern of drought followed by rain lines up with other research on the topic.
In November 2023, BC Salmon Foundation wrote about the relationship to coho deaths and significant rainfall events.
During the periods of drought, 6PPD-quinone accumulates on the road surface. Then the rain comes and creates road runoff with deadly concentrations of the chemical.
Millard Piercy Watershed Stewards also measured 6PPD-quinone during the winter season, and saw lower concentrations of the chemical in the creek, Novak said. The dangerous levels were only noticed after rainfall events preceded by drought.
The weather conditions in May of 2021 were extraordinarily unlucky for the coho smolts in Piercy Creek. When the society sampled the fish again in 2022 and 2023, they counted no mortalities.
“In 2021, the fish were just at the wrong place at the wrong time and the wrong rain event,” said Novak.
In total that year, the group counted 3,749 coho migrating within the watershed to the ocean. While the 136 mortalities may seem low in comparison, the fact that all of the mortalities were in Piercy Creek shows that this specific location needs attention, Novak said.
Wherever there are cars, there will be 6PPD-quinone
Novak wants people to know that even though the Comox Valley isn’t a huge urban community like Seattle or Vancouver, the salmon here are still impacted by this chemical.
Climate change is contributing to an increase in unpredictable weather, and the group is already seeing changes in the migration and spawning patterns of the salmon.
“We are concerned,” said Novak.
“We want to really raise awareness here in the picturesque and lovely Comox Valley where everything seems to be perfect, we have a problem.”
The Discourse previously interviewed Hans Schreier, professor emeritus of Land and Water Systems at UBC to discuss these unpredictable weather patterns and their impact on farmers.
He said that these extremes – heavy rains and droughts – are connected to one another.
When ocean temperatures increase, it means more moisture in the air, which means more flooding. Heat waves and fires are also connected because B.C. summers are more dry and hot.
Any road that has traffic will have 6PPD-quinone, Novak emphasized.
“Salmon, especially in Piercy Creek, which is an 80-per-cent-urban creek, are under enormous cumulative pressure of development, drought, climate change, and then on top of it, you have an influx of toxins,” he said.
But it’s only very specific weather patterns at very specific locations that lead to mortality events like the one in 2021 at Piercy Creek. And that clarity around the specific cause is good news, because it creates opportunities for interventions.
A water sample is taken at Piercy Creek. Photo courtesy of Millard Piercy Watershed Stewards
Wrong place wrong time, but solutions exist
Milliard Piercy Watershed Stewards will be putting up a smolt fence again in April to monitor this year’s juvenile coho. They’ll be investigating the impacts of 6PPD-quinone specifically, not just at Piercy Creek but also at a couple of other key locations where road runoff enters the watershed.
The good news? It is possible to mitigate the amount of 6PPD-quinone that seeps into waterways.
Research from UBC, Concordia and Vancouver Engineering services found that field-scale bioretention systems, also known as rain gardens, are effective in capturing 6PPD-quinone in stormwater.
Rain gardens are a type of filtration system that can be used in urban areas in which plants and soil are landscaped in a specific way to act as a sponge and capture and clean rainwater from the streets and sidewalks.
They catch sediment, remove pollutants and can also reduce erosion and improve groundwater. Courtenay already has some rain gardens on 5th Street.
Two UBC researchers conducted a local test on water containing 6PPD-quinone that drained through one rain garden in Vancouver and found that the garden filtered all but two to five per cent of the chemical.
Running a computer model after their initial test, the researchers predicted that the rain garden “would prevent more than 90 per cent of the chemical from directly entering salmon-bearing streams in an average year.”
The study says that finding safer alternatives than 6PPD in tire manufacture is a better long term solution, but bioretention systems are an effective solution in the meantime.
Novak says that he’s certainly curious about what tire companies are doing to mitigate this at the manufacturing level, but until things change on that end he hopes the Comox Valley can start using these types of bioretention systems to filter road runoff before it enters streams.
“The ultimate objective from our point of view, and I’m sure we’re not the only one, is to initiate mitigating activities. And we can do it ourselves.”
Filtering the runoff from the Comox Valley Parkway would involve cooperation from the Ministry of Transportation and Infrastructure, which is their responsibility, Novak said. But at other key locations, local governments can make a difference. For example, runoff from Willemar Ave, where relatively high concentrations of 6PPD-quinone have also been found, is within the jurisdiction of the City of Courtenay.
For now, Millard Piercy Watershed Stewards are gearing up for their 2024 fish count and are continuing to learn more about the best ways to ensure the juvenile salmon population makes it to the ocean as safely as possible.
Those hoping to learn more about Millard Piercy Watershed Stewards can go to their Facebook Page. More of Comox Valley’s conservation organizations can be found on the Comox Valley Conservation Partnership’s website.
There will also be a 6PPD-quinone workshop in Nanaimo at the end of April, organized by the BC Conservation Foundation. Registration is currently full, but those hoping to get on a waitlist can do so here.
Madeline Dunnett, Local Journalism Initiative Reporter, The Discourse
Local Journalism Initiative
