Going to blog about something that comes up every year about this time. I have had a few phone calls and messages about it already. . . .
Every year about this time we get reports of dead crappies or dead bluegills on a variety of waters. It is understandable that folks are concerned when they see dead fish. Of course assumptions are always the worst, that there has been some pollution event or there is something “bad” in the water. Most of the time, that is not the case. Most fish die-offs are due to natural causes.
When we see die-offs that are comprised of just one species of fish, maybe two related species, that suggests some kind of disease outbreak. With bluegills and crappies, remember those are warm-water species. Winter is hard on all living creatures and especially warm-water species of fish. They can be stressed coming out of the winter. Nebraska’s schizophrenic spring weather with wild temperature swings can add more stress to those fish. Then, as spring advances, crappies and bluegills undergo the rigors of spawning–more stress. All of that stress adds up and stressed fish are more vulnerable to bacterial infections. Fungal infections also occur secondarily, after the fish become “sick”. If you see stressed or dead fish with an ugly gray “fur” growing on them, that is a fungal infection.
Yes, those disease outbreaks result in some mortality. Keep in mind that fish populations in the wild experience significant natural mortality all year long, every year. In fact, natural mortality rates of panfish species can exceed fifty percent per year. “Mother Nature” is a cruel witch.
The important thing to remember is that there are fish that survive, enough to keep the population going healthy and strong.