welcome, like the name, I agree with comments. If you can an electrosurvey is money well spend. However also you can start by running some relative weights on your bass.
http://www.lakework.com/articles.phpBottom of this page will tell you how to do this. This will tell you if they are skinny for their size, thus removal is neccesary. Yes threadfin shad will be a big help for you, but only if yo plan to keep the pond fairly fertile. However harvest must be a part of this program and never a better tiem to start than the present.
jsas, if you got the bass out that easy I think you need to take more, tough call the first year on rec. #. You should see a major reduction in numbers caught if not keep pulling them out.
