Changing salmon hatchery release practices can improve survival rates: B.C. study
A first-of-its kind study in British Columbia suggests salmon hatcheries could improve survival rates by optimizing the weight of the juvenile fish and the timing of their release.
More than five billion juvenile salmon are released from hatcheries into the North Pacific Ocean each year, with about six per cent coming from B.C. and Yukon.
The hatcheries are aimed at stabilizing declining populations of wild salmon while keeping fisheries afloat, but the study says there’s a lack of robust scientific assessment of their overall efficacy for conservation purposes.
The study published in the Canadian Journal of Fisheries and Aquatic Sciences analyzed data from 21 chinook and 16 coho hatcheries in B.C. over the last two decades, finding higher survival rates were linked to heavier weights upon release.
For ocean-type chinook, it found the average maximum survival stemmed from releases six to 27 days earlier than historical averages for most of the hatcheries.
Meanwhile, coho survival rates could be improved by releasing the fish eight to 33 days later than the historical average.
The locations of hatcheries in the study ranged from Prince George, Revelstoke and the Fraser Valley, to the Sunshine Coast and Vancouver Island.
The findings do not represent a one-size-fits-all solution across hatcheries, says lead author Sam James, a biologist with the Vancouver-based Pacific Salmon Foundation.
The study found the greatest improvements in salmon survival rates were generally predicted from a combination of the optimal weight and timing of release.
Optimizing hatchery release practices could increase salmon returns by six to as much as 245 per cent for chinook and five to 160 per cent for coho, the study suggests.
However, James says it's important to look at full range of those possibilities, rather than focusing on the highest potential increases.
There were many locations for which changes were not expected to yield major increases in salmon survival and returns, and there was a high degree of uncertainty in the modelling around the ranges of potential gains, she says.
James says the study is unique because the researchers used an approach that examined numerous hatcheries as a group, allowing them to "unveil" the overarching relationships between release practices and survival while accounting for hatchery-specific deviations from the trends they identified.
Isobel Pearsall, the director of the Pacific Salmon Foundation’s marine science program, says the study is the first in B.C. to examine the efficacy of release practices on that larger scale.
“There were a couple of reports, lots of scattered information,” she says.
But there was no pre-existing larger study looking at different hatcheries together, and identifying release practices that could support higher survival rates, she says.
Salmon face many threats, James says, and while hatcheries cannot control conditions in the ocean, they can set the fish up for greater success with the right release practices.
The study did not consider economic factors, and additional expenses may be associated with optimizing release practices, Pearsall adds.
For example, it may be a challenge for hatcheries to increase the weight of juvenile chinook while also aiming to release them earlier, she says.
The researchers took into account the effects of other factors that can affect salmon survival rates, such as predators and environmental conditions, in order to focus their analysis on the role of release practices, she notes.
This report by The Canadian Press was first published March 24, 2023.
CTVNews.ca Top Stories
Spectacular aurora light show to be seen across Canada Friday night
A rare and severe solar storm is expected to bring spectacular displays of the northern lights, also known as aurora borealis, across much of Canada and parts of the United States on Friday night.
Town of Fort Nelson, B.C., ordered to evacuate due to wildfire
The entire town of Fort Nelson, B.C., as well as the nearby Fort Nelson First Nation, has been ordered to evacuate due to an out-of-control wildfire.
Snowbirds in Vancouver for puck-drop flyby as Canucks face Oilers
The Canadian Forces Snowbirds will be performing a flyover across downtown Vancouver at the start of tonight's Stanley Cup playoff game between the Canucks and the Edmonton Oilers.
McGill University seeks emergency injunction to dismantle pro-Palestinian encampment
McGill University has filed a request for an injunction to have the pro-Palestinian encampment removed from its campus.
Which Canadian cities have the highest and lowest grocery prices?
Where you live plays a big factor in what you pay at the grocery store. And while it's no secret the same item may have a different price depending on the store, city or province, we wanted to see just how big the differences are, and why.
Swarm of 20,000 bees gather around woman’s car west of Toronto
A swarm of roughly 20,000 bees gathered around a woman’s car in the parking lot of Burlington Centre.
Video shows naked raccoon catching B.C. family by surprise
When Marvin Henschel spotted a strange and hairless creature wandering through a front lawn in B.C.'s Lower Mainland, he could barely believe his eyes.
Barron Trump declines to serve as an RNC delegate
Former U.S. President Donald Trump's youngest son, Barron Trump, has declined to serve as a delegate at this summer’s Republican National Convention, according to a senior Trump campaign adviser and a statement from Melania Trump's office.
Out-of-control wildfire prompts evacuation alert for Fort McMurray, Saprae Creek Estates Friday night
An evacuation alert was issued for two Wood Buffalo communities Friday night, as crews battled an out-of-control wildfire near Fort McMurray.