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
Cuban government apologizes to Montreal-area family after delivering wrong body
Cuba's foreign affairs minister has apologized to a Montreal-area family after they were sent the wrong body following the death of a loved one.
What is changing about Canada's capital gains tax and how does it impact me?
The federal government's proposed change to capital gains taxation is expected to increase taxes on investments and mainly affect wealthy Canadians and businesses. Here's what you need to know about the move.
Quebec nurse had to clean up after husband's death in Montreal hospital
On a night she should have been mourning, a nurse from Quebec's Laurentians region says she was forced to clean up her husband after he died at a hospital in Montreal.
'Anything to win': Trudeau says as Poilievre defends meeting protesters
Prime Minister Justin Trudeau is accusing Conservative Leader Pierre Poilievre of welcoming 'the support of conspiracy theorists and extremists,' after the Conservative leader was photographed meeting with protesters, which his office has defended.
Fair in Ontario, flurries in Labrador: Weather systems make for an erratic spring
"It's a bit of a complicated pattern; we've got a lot going on," said Jennifer Smith of the Meteorological Service of Canada in an interview with CTVNews.ca on Wednesday. "[As is] typical with weather, all of these things are related."
Boeing's financial woes continue, while families of crash victims urge U.S. to prosecute the company
Boeing said Wednesday that it lost US$355 million on falling revenue in the first quarter, another sign of the crisis gripping the aircraft manufacturer as it faces increasing scrutiny over the safety of its planes and accusations of shoddy work from a growing number of whistleblowers.
Police tangle with students in Texas and California as wave of campus protest against Gaza war grows
Police tangled with student demonstrators in Texas and California while new encampments sprouted Wednesday at Harvard and other colleges as school leaders sought ways to defuse a growing wave of pro-Palestinian protests.
Bank of Canada officials split on when to start cutting interest rates
Members of the Bank of Canada's governing council were split on how long the central bank should wait before it starts cutting interest rates when they met earlier this month.
Northern Ont. lawyer who abandoned clients in child protection cases disbarred
A North Bay, Ont., lawyer who abandoned 15 clients – many of them child protection cases – has lost his licence to practise law.