Here in Michigan the accepted pond bait fish is a hybrid of bluegill and green sunfish. I'm just curious as to whether these fish are sterile (unable to reproduce) or not?

From the Diveristy of Fishes, Helfman et al. 2000.

"Most natural hybrids are inefficient reproductively, ecologically, biochemically, physiologically, or behaviorly. They are therefore likely to be reproductive failures because of sterility, relatively infertility, or an inability to find mates, or will be ecological failures because they will be outcompeted for resources or be more prone to capture by predators than are individuals from single-species matings. Natural selection will obviously favor spawning individuals that avoid mating with members of other species."

In other words, yes sometimes they are sterile. However, stressed fish, a system will multiple species of similar families, and a system with a large population of one species and a small population of another will hybridize. Nature is a finicky thing and fish will reproduce and backcross, but hopefully "natural selection" takes care of these fish.

Hope this helps.

I have a pond full of the fricken cross breeds. I was told 97% were male so there would be little chance of spwaning. The pond was sterile when I stocked it, I also stocked fathead minnows.

Well I have a pond full of green sunfish with big mouths and bluegill colors.

After 3 years I have yet to catch a F-1 over 4 inches. and hell no that ain't sterile, these breed three times a year.

I recently stocked 10 flathead catfish and 20 largemouth bass to remmedy the bream problem.

Next time its pure gills!!!