08/22/2026
Unfortunately, if you have been out to Corydon Lake the past couple days you would have been greeted by a gruesome sight; floating, dead fish.
The DNR has been notified, and they are looking into the cause of this mortality event.
It may have been just simply too warm of water, or possibly a surge in algae growth. Why would this kill the fish?
Fish still need to breathe oxygen, they just do it by absorbing it out of the water around them through their gills. Cold water is able to hold more dissolved oxygen, while warm water holds less. With long stretches of very hot days, the lake heats up, doesn’t get a chance to cool down, and has less oxygen. Very warm water can also be stressful for fish. Less dissolved oxygen and stressed fish means it’s more likely for fish to suffocate.
Another potential cause of low oxygen is a surge in the algae population. Every healthy lake needs some algae, it’s when the population explodes that it causes problems. Large mats of algae at the surface decrease the oxygen in the water under them, and then cause further problems as the algae dies and sinks, as the bacteria that eat dead algae then increase due to the sudden feast. These algae-gobbling bacteria use up oxygen in the water, leaving very little or nothing for fish to breathe.
Algae overgrowth can be caused by multiple things; warm, stagnant water, not enough rain, and sudden heavy rain that causes nutrients to increase in the lake.
The local Bald Eagles probably think this is the best day of their lives and have very full bellies. But for those that DON’T associate the smell of rotting fish with dinner, Corydon Lake is not very pleasant to be around right now. There will be an update as soon as we know more.
