What is winter-kill, and why does it shape so many perch lakes?
In shallow, fertile lakes under months of snow-covered ice, photosynthesis stops, decomposition keeps consuming oxygen, and by late winter the whole lake can slip below what fish survive — that is winter-kill, a fact of life across the northern prairies and countless small Canadian and upper-Midwest waters. Perch tolerate low oxygen better than most of their predators, and their boom-style spawning refills a lake within a few years, so winter-kill waters are often perch-dominated by default. The honest catch: big fish, with more mass to keep oxygenated, die first — which is why such lakes tend to cycle between stunted swarms and, in the few years after a partial kill thins the crowd, surprisingly fast-growing survivors.
The full story
This answer is one piece of a longer lesson — setups, diagrams and the reasoning behind it.
More questions about Breathing & oxygen
Same topic, other species
- Where do crappie go in late winter under the ice? — Crappie
- How does the thermocline affect where largemouth hold in summer? — Largemouth Bass
- What is the late-summer oxygen squeeze? — Muskellunge (Muskie)
- What is winterkill, and why does it matter for pike lakes? — Northern Pike
- Does a summer smallmouth have to move deep? — Smallmouth Bass
- What is a "summer squeeze" or summer kill for trout? — Trout (Rainbow · Brook · Lake)
- Why are walleye sometimes suspended out over the open basin? — Walleye