The effort to save one of Canada’s most endangered freshwater fish now involves electronic tracking of captive-bred and released specimens in the Nova Scotia watershed that is home to the world’s only remaining wild population.
Last week, a final batch of 30 tagged Atlantic whitefish were released into the Petite Rivière system behind the town of Bridgewater on the province’s south coast.
“We have released fish in different parts of the system, the lake part, the river part and also in the estuary in saltwater,” said Jeremy Broome, a Fisheries and Oceans Canada biologist assigned to the recovery team.
“So it’s important for us to see which one of them might produce the best survival.”
Needle Inserted Labels
Tiny transponder tags were inserted with a hypodermic needle into 150 spawning yearlings at Dalhousie University’s Aquatron marine research facility in Halifax.
The fish were anesthetized, given a week to recover, and released at various locations within the basin. The fish were released into the estuary after acclimating to salt water.
Devices installed in tight spots along the river system will send out a signal when a tagged fish swims past.
“We’re trying different approaches, spreading our eggs into different baskets to see what might work best,” Broome said.
“If we can determine that survival is better with estuary releases, we are seeing more fish coming back from that strategy, which would be an indication that we would want to continue with that approach.”
Landlocked for a century
This species of whitefish is an ancient relative of Atlantic salmon and naturally anadromous, meaning they hatch in freshwater, travel to the ocean, and return to spawn.
They have only survived in the Petite Rivière Basin, which was enclosed for a century by a dam and serves as the water supply for the city of Bridgewater.
A fish ladder was built there in 2012.
The recovery team hopes to see evidence that 150 untagged juveniles released last year and those tagged in 2023 return to spawn in one to two years.
Why Atlantic whitefish are in trouble
Nearly 40 years ago, the species was the first fish in Canada to be assessed as endangered by the Committee on the Status of Endangered Wildlife.
Whitefish face several threats, including warming waters and invasive smallmouth bass and pike introduced to the basin.
Atlantic whitefish are now so rare that when they are found, the young are brought an hour away to the Aquatron, where a captive breeding program is taking place.
Unlike previous years, no juvenile or larval whitefish were caught in traps set up throughout the system this spring.
Dalhousie’s Aquatron now contains more Atlantic whitefish than exists in nature.
“Without the breeding stock that we’ve been able to develop at that facility and the progeny that come from there now, we really wouldn’t have a choice. We’re not in a great place yet, but without that facility and without that program we’d be in a very dire place.” Broome said.
looking for another home
The recovery team is also looking at other watersheds in Nova Scotia where critically endangered species may be introduced and survive.
Several candidate sites have been identified and surveys are planned for this summer. Consultations are the next step.
“I think we’re at a point where we have to make a move and we have to start testing these things,” he said.
A 20 year old recovery merry-go-round
After it was first declared a species at risk in 2003, a captive breeding program was established at the Mersey Biodiversity Center in Nova Scotia as part of a government-mandated recovery strategy.
The program was closed and the Mersey diversity center was literally demolished under the Harper government in 2013.
Several months later, the voracious invasive chain pike was discovered in the Petite Rivière Basin, which was home to the remaining wild population.
Thousands of whitefish bred at the center of diversity had been released into a retention lake behind the Burnside industrial park in Dartmouth. None survived.
No living adult whitefish were seen between 2014, when the chain pike became established, and 2018.
dalhousie to the rescue
Dalhousie has since stepped in to offer his Aquatron facility, first as a Noah’s Ark to save the species from extinction and then to house a captive breeding program.
The university was also involved in building a creekside breeding facility, a miniature component of the diversity center that was demolished by the previous federal government.
Even the reintroduction into the Petite Rivière system is a repeat of the work of the canceled captive breeding program.
Still, Broome remains hopeful.
“This is truly, this is a Nova Scotia species of fish. It’s only found here, only in the province, the only place in the entire world,” he said.
“So it’s ours to do something about it. It’s ours to protect it and keep it on the face of the planet.”