We proceed our annual have a look at what makes this season particular, a time when nature isn’t just shutting down for 3 months. Right now the Science of Winter asks how fish can survive beneath the ice.
“Summer time is when biologists are likely to do area work,” says Steven Cooke, who would know. He’s a fish biologist at Carleton College, and he has been investigating what occurs to fish through the coldest season, when they’re locked away from air and light-weight.
Unhealthy issues, generally. However totally different fish deal with it alternative ways.
First comes the issue of small, shallow lakes that are likely to freeze over utterly and which don’t have loads of water to start with.
“Issues are likely to go badly when there’s loads of snow cowl on prime of the ice,” Cooke stated.
Mild can’t undergo thick snow “and so that you don’t get photosynthesis. So there are not any crops producing oxygen, there’s no means for oxygen to return by the air-water floor as a result of it’s frozen, and all you have got is decay.”
On the underside, previous natural matter is being damaged down by microbes. And so they dissipate a lot of the restricted oxygen that is still underwater.
“Finally if there’s loads of snow cowl the microbes will suck up all of the oxygen and it’ll kill different species like fish,” he stated.
“We really get fairly intensive winter kills in Jap Ontario. In a given 12 months, particularly in small lakes, you’ll be able to lose nearly all of the fish inhabitants in winter. Winter is usually a essential drive in structuring fish communities.”
Some fish survive nicely in low oxygen: carp, brown bullhead. Others are extra delicate: trout, bass, muskie.
However Cooke says there’s a “cryptic” nature to the winter kill. The place are all of the our bodies?
He studied a small non-public lake one winter on the Queen’s College Organic Station north of Kingston, tagging fish with radio transmitters that confirmed their location.
“We got here again within the spring and couldn’t discover any of them. We regarded in our knowledge; rapidly the fish simply all stopped shifting round mid-February and we didn’t discover a single carcass. We figured round 95 per cent of all of the largemouth bass within the lake died, but we by no means discovered a physique.
“If we didn’t have these knowledge, I’d have thought aliens got here and kidnapped the fish.”
He believes that the our bodies all sank.
In the meantime, rivers with open water in fast-moving sections can carry issues of their very own.
“What occurs on actually chilly nights the place you have got turbulence — so think about rapids — and also you get one thing occurring known as frazil ice.” This can be a assortment disks or small platelets of ice combined with the supercooled water.
“It will definitely gloms collectively and goes to the underside. But in addition, for those who’re a fish sitting there, it comes at you. It’s like attempting to breathe when you’ve got oatmeal coming at you.”
Fish soak up water by their mouths on the way in which to their gills. Frazil ice “is a bodily stressor as a result of, as they’re attempting to breathe, their mouths could be stuffed up with this frazil ice. It tends to be these actually chilly nights. It doesn’t occur on a regular basis.”
This ice could be pushed downward the place it builds up an ice layer hooked up to the river backside, often called anchor ice. This could drive fish to maneuver to a different location.
One other winter thriller is why some species of fish collect collectively in clusters. There are good causes, he notes, why ice fishing huts are in clusters, and it isn’t to share the drinks.
Bass particularly do that. “Ninety-nine per cent of the water in a given water physique may have zero bass in it.
“We actually don’t know what makes a very good winter aggregation website.”
Some fish hold shifting extra actively than others in winter. “Some fish are simply chilling out; they actually gradual issues down. Their coronary heart price is possibly two to 4 beats a minute” — not hibernating, however “actually they simply sit there. They don’t even eat. They’re sitting on the underside behind their favorite rock” except ice pushes them out.
These species, resembling bass, can be simple prey for pike and walleye, which keep energetic.
Cooke has a Canada Analysis Chair in environmental science and biology.
ALSO IN THE NEWS
Why ice storms occur so typically in Ottawa
Freezing rain, stopped trains, service enchancment: An LRT Q+A with Ottawa’s director of transit operations
Injury to Eddy constructing forces detours in Gatineau