07/18/2026
🐟 Why We're Seeing Dead Carp, Tullibee, and other fish on Lake Koronis Right Now
If you've noticed carp/Tullibee turning up along the shoreline lately, there's real science behind it, and it comes down to a simple problem: warm water just can't hold enough oxygen.
Here's what's happening:
🌡️ Warm water physically holds less oxygen. Water at 90°F can only hold about 7.4 mg/L of dissolved oxygen at full saturation. Water at 45°F can hold 11.9 mg/L — over 60% more. As our lake heats up through the summer, the oxygen "ceiling" drops with it.
🐟 Warm-acclimated fish need MORE oxygen, not less. Research on common carp specifically has found that fish acclimated to warmer water lose equilibrium at oxygen levels 36% higher than fish acclimated to cooler water. So right when the lake has the least oxygen to offer, carp need the most.
💀 35°C (95°F) is where things turn dangerous. Studies on common carp show they handle 27°C (80.6°F) and 31°C (87.8°F) reasonably well, but at 35°C (95°F), it becomes physiologically stressful enough to cause cellular damage — including measurable abnormalities in their red blood cells.
🌙 Overnight is often the worst window. During the day, algae and aquatic plants pump oxygen into the water through photosynthesis. Once the sun goes down, that stops — and respiration by all that plant life starts pulling oxygen back OUT of the water instead, all night long. Oxygen levels bottom out right before dawn, which is why die-offs are often discovered in the morning.
The combination of a hot stretch of weather + a heavy plant/algae load in shallower parts of the lake is a textbook setup for exactly what we're seeing. It's not pollution or disease — it's basic water chemistry catching up with the fish during the hottest part of the year.
If you're out on the water, this is a good reminder of why shoreline aeration, healthy w**d management, and keeping an eye on shallow bays during heat waves all matter for lake health. 💙
