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
Indian envoy warns of 'big red line,' days after charges laid in Nijjar case
India's envoy to Canada insists relations between the two countries are positive overall, despite what he describes as 'a lot of noise.'
Stormy Daniels describes meeting Trump during occasionally graphic testimony in hush money trial
With Donald Trump sitting just feet away, Stormy Daniels testified Tuesday at the former president's hush money trial about a sexual encounter the porn actor says they had in 2006 that resulted in her being paid to keep silent during the presidential race 10 years later.
U.S. paused bomb shipment to Israel to signal concerns over Rafah invasion, official says
The U.S. paused a shipment of bombs to Israel last week over concerns that Israel was approaching a decision on launching a full-scale assault on the southern Gaza city of Rafah against the wishes of the U.S.
Former homicide detective explains how police will investigate shooting outside Drake's Bridle Path mansion
Footage from dozens of security cameras in the area of Drake’s Bridle Path mansion could be the key to identifying the suspect responsible for shooting and seriously injuring a security guard outside the rapper’s sprawling home early Tuesday morning, a former Toronto homicide detective says.
Northern Ont. woman makes 'eggstraordinary' find
A chicken farmer near Mattawa made an 'eggstraordinary' find Friday morning when she discovered one of her hens laid an egg close to three times the size of an average large chicken egg.
Susan Buckner, who played spirited cheerleader Patty Simcox in 'Grease,' dead at 72
Susan Buckner, best known for playing peppy Rydell High School cheerleader Patty Simcox in the 1978 classic movie musical 'Grease,' has died. She was 72.
Jeremy Skibicki has 'uphill battle' to prove he's not criminally responsible in Winnipeg killings: legal analysts
Accused killer Jeremy Skibicki could have a challenging time convincing a judge that he is not criminally responsible for the deaths of four Indigenous women, a legal analyst says.
Bye-bye bag fee: Calgary repeals single-use bylaw
A Calgary bylaw requiring businesses to charge a minimum bag fee and only provide single-use items when requested has officially been tossed.
Alcohol believed to be a factor in boating incident after 2 men die: N.S. RCMP
Two Nova Scotia men are dead after a boat they were travelling in sank in the Annapolis River in Granville Centre, N.S., on Monday.