Over a dozen Atlantic salmon were released into the Clyburn Brook as part of a salmon restoration project in October.
Salmon populations in the brook — located in Cape Breton Highlands National Park– have declined by over 95 per cent since 1991.
“We released 18 salmon; we haven’t counted that many come back since 2003,” resource management officer and coordinator of the highland branch of the salmon restoration project, Sarah Penney said.. “So, 18 doesn’t sound like a lot, but in the context of decades of fewer than 20 fish returning to spawn it’s actually pretty significant.”
The minimum requirement for conservation purposes is 75 Atlantic salmon returning to spawn each year.
Each November, researchers don their snorkel gear and dry suits to scour the river and do a count of the returning salmon. The highest number on record since they started keeping track was 175 fish in 1987.
Cape Breton Highlands National Park resource conservation specialist, Sarah Penney, collecting juvenile salmon in spring to be taken to Dalhousie’s Aquatron Lab. Photo Courtesy: Parks Canada
It’s hard to pinpoint what’s causing population decline, Penney said. Though she speculated climate change may be playing a role.
She also noted, it’s hard to say what effect population declines will have on the rest of the river.
“When they spawn and when they die and when they’re eaten by predators, all those nutrients they’re bringing with them are contributing to productivity in the river — the insects and the plants and the other life that lives there, as well as the forest around.”
The restoration project began in 2019, though other national parks, such as Fundy, Gros Morne, Terra Nova and Kouchibouguac have been doing it for longer.
“[Fundy National Park has] seen an increase in the number of adults returning,” Penney said. “They’re at a 30 year high in terms of adult returns. So, We’re learning from them and building on the success that they’ve had.”
The fish were caught as smolt and raised at Dalhousie’s Aquatron Laboratory, a land based research facility, before being transported back to the Clyburn Brook, where they were born.
In early October, a month ahead of spawning season, the fish were released into a pool in the brook to acclimate before starting the journey upriver.
They need a month to acclimate because salmon take signals from their environment on when to spawn — something that’s hard to replicate in captivity, Penney said.
Each has a tag placed just under their skin, about the size of a grain of rice, so researchers can monitor how many salmon return over the coming years.
Penney expects they’ll see the spawn of these 18 salmon return to the brook in the fall of 2023-24
They’ll know by 2025 whether subsequent generations are returning.
