Thanks guys.

In hindsight and with the helpful info you provided, I am now convinced that the carp I caught were in fact grass carp.

The water body was badly overgrown with alge and I was actually fishing it to see if I could get any good sized bluegills or redears out of it. No such luck: the only thing I caught was grass carp. I remember being suprised because I fished using worms, and I know there once was a sizable bluegill population in the lake.

The carp I caught were small, it will be interesting to see if next summer they have been able to grow in size and/or keep the alge and weeds at bay in this public lake.

I suspect that farm runoff has made this body of water (10-15 acres) so highly fertilized and silted so that no amount of grass carp intoduced by the DNR or some other source can keep the plant growth under control.

Has anyone else ever seen a lake that would not respond to the introduction of grass carp? This lake has been overgrown with alge and weeds for the last 10 years or so.

Thanks again for the info.