UBC researchers map Pacific salmon habitat, finding much is lost or inaccessible
Pacific salmon can no longer access hundreds of kilometres of spawning streams or floodplain habitat after decades of urban, agricultural and resource development around British Columbia's Lower Fraser River, a study has found.
The study and mapping by researchers at the University of B.C. focused on 14 populations in the lower stretch of Canada's most productive salmon river.
It maps where an estimated 85 per cent of floodplain is dried up or inaccessible to salmon due to dikes, along with 1,700 kilometres of streams thought to be “completely lost” due to in-filling and barriers such as dams and road culverts.
The study used earlier research from the University of B.C. that examined surveyors' notebooks detailing vegetation in the late 19th century to map floodplain areas that would have been available to salmon, said Riley Finn, the study's lead author and a research assistant at UBC's conservations decisions lab.
Such vegetation-rich habitat is crucial for salmon species that remain in fresh water for some time after eggs are hatched, such as chinook and coho, Finn said.
“When those waters come up on an annual basis, it provides terrestrial insect input, so that's a new food source they can go and forage after. It also provides protection from predation. So it's really important in this juvenile rearing phase,” he said.
Finn's study, published in the journal Ecosphere in July, identified the vegetation that was likely to withstand annual flooding and compared it to current dike mapping.
Just over 100 of an estimated 659 square kilometres of historical floodplain habitat remains accessible, with some variation for different salmon populations, it found.
Sumas Lake, for example, is currently kept dry to support farming through a series of canals and pumps after being drained in 1924, the study says. It considers the dry lake historical floodplain habitat due to accounts of wide variation in water levels, ranging from nine feet deep during winter to 36 feet deep in the spring.
It's another question altogether whether the floodplains would be accessible today had dikes never been built, said Finn, as salmon are struggling with other pressures, including the impacts of the climate crisis on their freshwater and marine habitats.
Fisheries and Oceans Canada announced in June the closure of nearly 60 per cent of commercial salmon fisheries during this year's season, saying in a statement “Pacific salmon are in a long-term decline, with many runs on the verge of collapse.”
The department attributed the declines to “a complex combination of climate change, habitat degradation, and harvesting impacts,” and added that “bold action (was) needed now to stabilize and rebuild the stocks before it is too late.”
The study also mapped and estimated the extent of blocked and lost salmon streams, finding over 1,200 barriers interrupting 2,200 kilometres of streams, with 1,700 kilometres thought to be entirely lost from the landscape.
Overall, that represents about 64 per cent of the estimated 6,118 kilometres of streams that would otherwise be naturally accessible in the Lower Fraser, it says.
The 14 salmon populations considered in the study include two that have been assessed as endangered by the Committee on the Status of Endangered Wildlife in Canada, three that are considered threatened and one of “special concern.”
Tara Martin, a professor at the University of B.C.'s faculty of forestry who leads the conservations decisions lab, said if salmon don't have sufficient habitat to breed and complete their life cycle, then other conservation efforts won't matter.
“Given the magnitude of habitat loss in the Fraser, large-scale habitat protection and restoration is a key component in efforts to restore wild populations.”
The new study provides a foundation for Finn's ongoing work at the lab to identify priority areas where removing in-stream barriers and restoring salmon habitat would be feasible and produce the greatest benefits for salmon recovery, he said.
This report by The Canadian Press was first published Aug. 14, 2021.
This story was produced with the financial assistance of the Facebook and Canadian Press News Fellowship.
CTVNews.ca Top Stories
Walking pneumonia is surging in Canada. Is this unusual?
CTVNews.ca spoke with various medical experts to find out the latest situation with the typically mild walking pneumonia in their area and whether parents should be worried.
Joly, Blair condemn anti-NATO protest in Montreal that saw fires, smashed windows
Federal cabinet ministers condemned an anti-NATO protest in Montreal that turned violent on Friday, saying 'hatred and antisemitism' were on display, but protesters deny the claim, saying they demonstrated against the 'complicity' of NATO member countries in a war that has killed thousands of Palestinians.
Retiring? Here's how to switch from saving for your golden years to spending
The last paycheque from a decades-long career arrives next Friday and the nest egg you built during those working years will now turn into a main source of income. It can be a jarring switch from saving for retirement to spending in retirement.
'Her shoe got sucked into the escalator': Toronto family warns of potential risk of wearing Crocs
A Toronto family is speaking out after their 10-year-old daughter's Crocs got stuck in an escalator, ripping the entire toe area of the clog off.
Ottawa driver fined for hauling thousands of empty cans in trunk of car
Ontario Provincial Police stopped an Ottawa man for dangerously hauling thousands of empty cans from the back of his car.
Canada's top general takes on U.S. senator in defending womens' role in combat units
Canada's top general firmly rejected the notion of dropping women from combat roles -- a position promoted by president-elect Donald Trump's nominee for defence secretary -- at a security forum underway in Halifax on Saturday.
Canadians are craving to take a 'adult gap year.' Here's why
Canadian employees are developing an appetite for an 'adult gap year': a meaningful break later in life to refocus, refresh and indulge in something outside their daily routine, according to experts.
Transit supervisor assaulted with 'torch' made of hairspray can and lighter: police
A Winnipeg man has been charged after a transit supervisor was assaulted with a makeshift torch in the city’s downtown area Friday morning.
Prime Minister Trudeau attends Taylor Swift's Eras Tour in Toronto with family
Prime Minister Justin Trudeau is a Swiftie. His office confirmed to CTV News Toronto that he and members of his family are attending the penultimate show of Taylor Swift's 'The Eras Tour' in Toronto on Friday evening.