B.C. study links low river flows with lower chinook salmon productivity
A study that links low summertime water flows in a British Columbia river with lower productivity across 22 generations of a struggling salmon population could help guide how rivers are managed to support fish, the authors say.
The study published Friday in the journal Ecological Solutions and Evidence used data from 1992 to 2013 to examine changes in the productivity of early summer chinook in the Nicola River, a tributary of the Thompson River in B.C.'s southern Interior.
The modelling predicted fish that were spawned and later reared when the river's flows in August were 50 per cent below average had a 29 per cent lower productivity rate, referring to the number of offspring produced per spawning fish that survive to adulthood.
“The significance of this work is that we've been able to disentangle the influences of freshwater conditions from ocean conditions and really show that freshwater conditions are very important for this population,” said lead author Luke Warkentin.
Adult chinook return to the river from the ocean to spawn, while their offspring spend a year in fresh water after hatching from eggs deposited in gravel nests.
“August is a really critical month, because you have low flows, you have fish coming in, holding and waiting to spawn, and you have high air and water temperatures,” said Warkentin, who completed the research while studying at Simon Fraser University and now works as a biologist with Fisheries and Oceans Canada.
The lower flows combined with high air temperatures mean the water heats up more quickly, to the point that it can be harmful to salmon, while also reducing the availability of deeper, cooler pools where the fish take refuge, he said.
Overall, the Nicola's average August flows were about 26 per cent lower during the two-decade study period than in the early part of the 20th century, the study notes.
It attributes the decrease to the impacts of climate change, water withdrawal and land use, such as logging, farming and urban development.
Warkentin said he hopes the study's findings will support a more holistic understanding of water management for the Nicola, recognizing the impact of low flows on a salmon population that's been assessed as endangered by the Committee for the Status of Endangered Wildlife in Canada.
The province manages the Nicola River's flows, working with federal fisheries officials, First Nations and other local authorities, while considering snowpack, water levels in lakes and reservoirs, the severity of any drought and demand from nearby communities and agricultural operations.
There is no set amount of water to support a healthy salmon population, said Richard Bailey, a retired Fisheries and Oceans biologist who contributed to the study.
Rather, the right flow is the one that creates the best opportunities for the fish to survive while taking into account surrounding conditions, he said, including air temperatures and the effects of wildfires and different land use.
Changes in the mountainous upper reaches of a watershed significantly affect the timing and intensity of spring runoff and the duration of drought, Bailey noted.
Melting snow and rain run more quickly off slopes that have been logged or scorched by wildfire, bringing sediment that clogs spawning grounds, raising the risk of flooding and leaving little water to trickle down over the summer, he said.
Re-establishing trees and vegetation higher in a watershed is crucial for rehabilitation work below, along riverbanks and floodplains, Bailey added.
The modelling also demonstrated that generations of Nicola chinook incubated during years with significant fall flooding had lower productivity, as floodwaters can crush or scour salmon eggs from the riverbed, Warkentin said.
The finding doesn't bode well for eggs that were incubating before last November, when a series of atmospheric rivers deluged southwestern B.C., causing widespread flooding. The Nicola River swelled and carved a new course, swallowing homes and chunks of the highway between Merritt and Spences Bridge.
“The flood in November was larger - based on the preliminary numbers I've seen - was larger than any of the floods on record in the fall that we looked at,” Warkentin noted.
The Committee for the Status of Endangered Wildlife assessed Lower Thompson chinook as endangered in November 2020, including those that spawn in the Nicola. It recommended the population be listed under the Species at Risk Act, noting a “steep decline” in the number of mature fish from 2013 to 2018.
The chinook face numerous severe threats in their freshwater and marine habitats, including the effects of logging following an extensive outbreak of mountain pine beetle, wildfires, water withdrawal and climate change, the committee found.
It's up to federal cabinet to decide whether to list any species as threatened or endangered, designations that carry prohibitions against destroying critical habitat.
This report by The Canadian Press was first published Jan. 21, 2022.
CTVNews.ca Top Stories
NEW From yearning for a change to cost of living, why some Canadians have left or may leave the country
For some immigrants, their dreams of permanently settling in Canada have taken an unexpected twist.
Here are the ultraprocessed foods you most need to avoid, according to a 30-year study
Studies have shown that ultraprocessed foods can have a detrimental impact on health. But 30 years of research show they don’t all have the same impact.
NEW Capital gains tax change 'shortsighted' and 'sows division' business groups tell Freeland
Forging ahead with increasing Canada's capital gains inclusion rate 'sows division,' and is a 'shortsighted' way to improve the deficit, business groups are warning Finance Minister Chrystia Freeland.
Ontario man frustrated after $3,500 paving job leaves driveway in shambles
An Ontario man considering having his driveway paved received a quote from a company for $7,000, but then, another paver in the neighbourhood knocked on his door and offered half that rate.
Defence attacks Stormy Daniels' credibility as she returns to the stand in Trump's hush money trial
Stormy Daniels will return to the witness stand Thursday in Donald Trump's hush money trial as the defence tries to undermine the credibility of the porn actor's salacious testimony about their alleged sexual encounter and the money she was paid to keep quiet.
With contactless screening tech, this Toronto startup hopes to catch breast cancer early — and save lives
Amid evidence of rising breast cancer rates among young women in Canada, one Toronto startup is offering a contactless and radiation-free device that can help doctors identify suspicious changes in breast tissue. The company, Linda Lifetech, says this can lead to earlier detection of breast cancer.
Tornadoes tear through southeastern U.S. as storms leave 3 dead
Forecasters warned a wave of dangerous storms in the U.S. could wash over parts of the South early Thursday, a day after severe weather with damaging tornadoes and large hail killed at least three people in the region.
Police handcuff man trying to enter Drake's Toronto mansion
Toronto police say a man was taken into custody outside Drake's Bridle Path mansion Wednesday afternoon after he tried to gain access to the residence.
What is whooping cough and should Canadians be concerned as Europe declares outbreak?
There is currently a whooping cough epidemic in Europe, with 10 times as many cases compared to the previous two years. While an outbreak has not been declared nationwide in Canada, whooping cough is regularly detected in the country.