Nova Scotian lakes and rivers in peril

The more diverse an ecosystem, the greater its resilience.
This is among the firmest precepts of biodiversity and one of my favourite. The more intact our wilderness, the more of its native species remain alive and well and active in the workings of ecology, the more prepared we will be for the incursion of invasive species plaguing North America, for the apocalyptic consequences of unfettered climate change, for the policies of regressive governments.
It’s as strong an argument for conservation as any I’ve ever heard, allowing us not only to maintain the functionality of the world which sustains us, but the beauty inherent within.
But not all of Nova Scotia is naturally biodiverse. While our protected forests and shorelines and coastal waters are veritable zoos, our freshwater ecosystems are remarkably simple, even when compared to nearby New Brunswick.
The variety of fish we host in our shallow lakes and rivers is naturally sparse, and therefore naturally vulnerable to human hazards. If any aspect of our natural heritage was in need of gentle and cautious treatment, it’s this.
“We have lost so much of our freshwater biodiversity in Nova Scotia and people don’t really known about it,” Paul Bentzen, a conservation biologist and geneticist with Dalhousie’s Life Sciences Centre, told me in late April.
The chief cause of this ongoing collapse, he says, is the introduction of invasive fish to watersheds across the province. In the 1940s, smallmouth bass were brought here legally from New Brunswick (where they are also not native) so anglers would have something to catch in July and August when native trout are less active. That same decade, people illegally introduced chain pickerel.
Since their arrival, both fish have been carried illegally from watershed to watershed by anglers eager to have these fish closer to home, imposing ravenous invasives on ecosystems in no way prepared to handle them. Over the decades both Smallmouth bass and chain pickerel have spread from Yarmouth to Cape Breton, eating everything that moves, from native fish to ducklings, from endangered turtles to threatened snakes.
Only recently, chain pickerel executed a thorough takeover of Kejimkujik National Park, conquering lakes once the secure domain of several species-at-risk. Across the province these invaders have devastated native brook trout, undoing any supposed benefit to anglers.
The last significant study reviewing the health of Nova Scotia watersheds dates back to the 1950s, and what few studies exist comparing this past abundance to the modern day are staggering. In many cases, says Bentzen, our freshwater ecosystems have been demonstrated to possess a fraction of their former abundance and biodiversity, but most of the picture remains missing.
“No one in the field doubts that we’ve suffered a major loss,” he says. “Into our simpler ecosystems we’ve introduced two top predators, which are running rampant.”
Once pickerel and bass establish themselves they are almost impossible to eliminate. The only successes I’m aware of involve scorched-earth tactics as yet unpractised in Nova Scotia. Our federal government has instead, for years, been electrifying infested lakes to stun their fish, removing invasives and leaving natives, but even this so-called “electrofishing” can only control invasives, not eradicate them, and as more watersheds fall, control measures become laughably inadequate.
So here we are, a freshwater crisis on our hands and precious few solutions.
One is, of course, to replicate the 1950s study in watersheds across Nova Scotia and get a true handle on what we’ve lost, something for which Bentzen is seeking funding.
But there’s also education. The message must reach every well-meaning angler, that the lakes and river providing them spiritual and dietary fulfillment are impossibly fragile, and cannot remain fruitful if invasive species are spread by way of buckets. What we need is a serious and concerted partnership between anglers, conservationists, and government to catch as many of these bass and pickerel as possible so native species can breath and perhaps, in time, recovery.
“It is illegal and immoral to move invasive species,” says Bentzen. “We need it to stop.”

This story was originally published in Halifax Magazine.

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