Lake Waubesa: Fisherman Charlie Turner says it's not a pretty sight along the shores of Lake Waubesa. "Along the shoreline there's a lot of dead bluegills. They've washed up on the shore and it smells pretty bad, but there's a lot of them."

They were killed by bacteria known as Columnaris.

"It's a bacterial disease. It attacks the gills and the skin of the fish," says DNR Fisheries Expert Scot Stewart.

Stewart says the bacteria is natural to the lake. Conditions are right when the water temperatures hits 65 degrees. The bacteria strikes every year.

Stewart says this year the spring was colder, pushing the fish kill back–making it even deadlier. "We had a quick warm up just recently. At the same time fish were coming in to spawn. When the fish are spawning they get beat up a little bit. They're concentrated, so you just set the stage for a real outbreak. And that's what we're seeing this year."

Columnaris bacteria destroy the gill tissue, preventing the fish from breathing. Diseased fish can be spotted by the sores on their sides. "It will be an opaque type circle. That opaqueness comes from the mucus thickening because of the bacteria attacking the skin," says Stewart.

Fisherman Ron Brown saw all the dead fish and he wasn't sure what killed them. "I guess that's why I don't eat them. It bothers me to see that and I don't know if it's doing something to the fish that we're catching. That's why I just catch and release and not eat."

Stewart says the fish are safe to eat, because cooking kills the bacteria. Even so, he says most anglers are not that hungry. "If you see a fish with a sore on its side it's not going to go in the frying pan."

If you see any substantial fish kill the DNR is asking you to call them. In Dane County call (608) 273 5946. In Columbia County call (608) 635 8122.