Let the lunkers go: New science explains why big fish matter so much

RESTORATION

To also ensure healthy populations of big fish, Tufts warns that maintaining natural fish habitat is overriding and non-negotiable. On many of the best salmon and trout rivers, for example, we have traded off the choicest rapids and riffles for hydro dams, and accepted hatcheries as a mitigation strategy. This approach has failed miserably.

“It speaks to some really serious issues we’re trying to grapple with these days, because we’re talking about species that are important to anglers,” Tufts says, pointing to the program to restore Lake Ontario’s extirpated Atlantic salmon population. “The challenges are incredible. Part of it is producing fish artificially in a hatchery, then releasing them and expecting them to know how to survive, what to eat, and how to flee predators—things that are learned behaviours.”

Rob Swainson, a retired brook trout biologist with the Ontario government, chuckles when I mention Tufts comments about protecting critical fish habitat. He recounts the time he walked into the Ontario Power Generation office at the Alexander Falls Dam on the Nipigon River, home of the world-record brook trout. It was 1988, and he naively told the workers he was going to put them out of business. “They laughed at me.”

The situation was dire, however, and the threat of imposing the Fisheries Act caught their attention. “When I stood on shore, I could see that the drawdown was over three feet from where the trout had spawned in the fall,” Swainson recalls these many years later. “The eggs were high and dry.” The world-class brook trout fishery, which was on its deathbed, was rejuvenated not a moment too soon.

These days, the river is being managed under a strict water-flow agreement that puts trout at the top of the priority list. Swainson now goes out of his way to compliment the OPG for recognizing the problem, then training staff and working tirelessly to address it.

Incredibly, the fact the Nipigon’s last few big old female brook trout were saved highlights another biological principle now coming to the forefront. According to Swainson, BOFFFFs have what is known as a “storage effect,” which allows them to maximize their energy reserves, survive tough environmental conditions and eventually spawn, producing an incredible number of high-quality eggs—if conditions finally improve.

HABITAT HELP Degraded spawning grounds are in desperate need of stewardship in order to get the most from big, old, fat, fertile, female fish, says Robert Pye, executive director of Watersheds Canada. “With the pressures from increased development, invading species and climate change, there’s never been a more critical time for lake stewardship education,” he says. “Waterfront property owners are the first line of defence for fish habitat, especially when they understand their naturalized shoreline can protect local spawning grounds from erosion and runoff.” Clearing spawning beds, revitalizing nursery areas using washed river stone and planting trees along cold-water streams, for example, can significantly support fish-management goals.