The entire global population of Atlantic whitefish is restricted to a single watershed in southern Nova Scotia, and in the minds of many, even this haven is no longer safe.
They used to be more widespread, of course, but impassable dams and invasive species destroyed their strongholds on the Tusket River, Yarmouth, and have prevented them from visiting the Atlantic Ocean, as some once did. Our surviving whitefish live a strictly freshwater existence, in three lakes on the Petite Rivière, Bridgewater.
These lakes are the Hebb, Milipsigate and Minamkeak in ascending order. Invasive Smallmouth bass and Chain pickerel have already inundated the lower two, imposing their considerable appetites on resident wildlife. The hold of whitefish on this watershed is, to say the least, tenuous.
“Once the pickerel are in Minamkeak Lake, which they will be before too long, it’s a countdown to extinction,” said Andrew Breen of the Bluenose Coastal Action Foundation. He ranks among the most active whitefish advocates in the province, and works daily to prevent their disappearance through on-the-ground research and conservation. He’s the one cutting open Smallmouth bass and recovering partially digested whitefish from their stomachs. One time, inside a Chain pickerel, he found two baby turtles, alive and well.
Breen makes it clear that the Petite Rivière is no longer safe for Atlantic whitefish. Bass and pickerel are being removed from these lakes by the thousands, through a joint electrofishing endeavour with the provincial and federal governments, but both of these veracious fish repopulate too quickly to be eliminated outright.
“We need to be looking at other watersheds free of invasive species where we can try introducing a few whitefish, somewhere they might persist,” said Breen. “They haven’t got much time left.”
This has been attempted, of course. In 2000, a captive breeding program at the Mersey Biodiversity Facility in Milton, Nova Scotia, was founded with five adult whitefish taken from Petite Rivière. Between 2005-2008 some 12,000 captive raised whitefish were introduced to Anderson Lake in Dartmouth – a choice Breen considers uninspired – and from 2007-2009 another 12,000 were released downstream in the Petite Rivière, in hopes of restoring their seafaring nature.
But with the abrupt closure of the Mersey Biodiversity Facility in 2012 by the Harper government, this captive breeding program was cancelled before it could produce meaningful results. The 12,000 released in downstream Petite Rivière apparently didn’t take, and more recent monitoring of Anderson Lake showed a complete absence of surviving whitefish. All hopes, and fears, returned again to the Petite Rivière.
From Whence They Came
That brings us to this spring, when the fragility of the Petite Rivière population forced the Department of Fisheries and Oceans (DFO) to take 28 whitefish youngsters – collected by Andrew and his colleagues – to the Coldbrook Hatchery.
Alain Vézina, regional director of science with DFO, called these 28 whitefish (25 of whom survived the summer) a “risk mitigation measure.” In short, they were trying to get all their eggs out of one basket. But no plan was in place for these young whitefish when they arrived at Coldbrook, and they couldn’t stay for long. Vézina said this hatchery is at capacity, and is not ideal for the housing of whitefish long term. Rumours flew in late September that these 25 refugees would be dumped back into their lake of origin by October’s end, because no better facility was available to take them.
“When I heard these fish were going back to their lake of origin, I knew I had to stop it,” said Dr Paul Bentzen, a geneticist with Dalhousie University and chair of its biology department. “I knew they were going to die there. The mortality rate would be very high, if not 100 per cent because of the pickerel and bass.”
Upon confirming this rumour over the phone with Vézina in mid October, Dr Bentzen offered to take the whitefish himself, and hold them at Dalhousie’s state-of-the-art research aquarium – Aquatron. According to Dr Bentzen, his offer was accepted and the paperwork was underway by mid October, transferring these 25 whitefish from Coldbrook to Aquatron. At the time of this posting in mid-December, the trade had yet to occur.
Precedent and Priorities
The Atlantic whitefish is not the first of its kind to be imperiled by failing habitat. Across the Atlantic Ocean, in the U.K., freshwater ecologist Ian J. Winfield of the Centre for Ecology & Hydrology, has participated in the translocation of both the Common whitefish (Coregonus lavaretus) and European cisco (Coregonus albula) for conservation purposes, both of whom share a genus with our Atlantic whitefish (Coregonus huntsmani).
These U.K. species were under threat by the alteration of their native habitat, pollution thereof or the introduction of invasive species. When their decline was considered too steep, and their range too restricted, both were translocated, establishing “refuge populations” in other lakes entirely in case the worst should happen at home. Some of these translocations were extremely successful, one proceeded by the collapse of its source population.
“Personally, I view refuge populations as an emergency measure,” said Winfield. “My preferred option is to remedy the issues facing a population in their original habitat…[but] if [invasive] species are the issue, it’s usually intractable. So, refuge populations have their role to play. In emergency cases, I think they should take priority.”
Winfield declined to comment on the situation of the Atlantic whitefish, given his lack of familiarity with its situation, but a state of emergency has been declared by both Breen and Dr Bentzen, among others.
“As much as I hate to say it, I think our whitefish are doomed in the Petite Rivière,” said Dr Bentzen. “I am reasonably certain that, in the end, the invasive predators win.”
Establishing whitefish in a watershed free of invasive species should be our long term conservation goal, in the opinions of both Breen and Dr Bentzen. A DFO Science Advisory Report on exactly this topic, published in September of 2018, said that such translocation would necessitate a captive breeding program, because it’s unclear how many whitefish remain in Petite Rivière.
“Immediate actions to establish self-sustaining populations of Atlantic Whitefish in invasive-free habitat could prevent extinction,” the report reads.
While Aquatron can easily host 25 Atlantic whitefish, Dr Bentzen said a captive breeding program is another discussion entirely, which would require a great deal of preparation, funding from the federal government and perhaps the involvement of Dalhousie’s Truro campus, better equipped to propagate fish by the thousands. For the time being, however, he will tap into research funding to keep these 25 whitefish alive, to study them, and even to sequence their genome; why not?
“There are thousands of lakes in Nova Scotia, tens of thousands if you look a little farther afield in the Maritimes and Newfoundland,” he said. “I have a hard time believing we couldn’t find some refuge habitat for these whitefish, at least for a freshwater population. [We’re facing] outright extinction of the species. I think some fortitude and courage in making decisions about what else can be done is really important, and it’s not clear that’s happening [at DFO].
“I’m determined to do everything I can to keep these 25 whitefish safe until a better solution presents itself. If there is no better solution, maybe these fish and their descendants will be at Dalhousie University for a long time. These fish are not getting put back in their original habitat, and they’re not to be sacrificed in any other way. We’ll do our best to take care of them.”
Zack Metcalfe is a freelance journalist, author, and writer active across the Maritimes. This article was originally published with Rural Delivery Magazine.