Hello fellow pond enthusiast you have found the right site. I was actually faced with a similar decision not to long ago. The options are protean: here are a few - one you could seine the pond and there are some good ways to do this and samples of such method are posted on this web site and in many books that describe basic pond management. This will allow you to get a better idea of exactly what is in the pond and their individual variations within their own lifecycle. Additionally you could kill off the ones that get trapped that are the undersirable say the ones under 6 inches and throw the bigger ones back in.

Another option is scrap what you have and start over - you could chemically kill the existing gills and start the whole process again. the obvious advantage is that you will be able to control the populations to certain extent if you know what you put in like hybrid gills and bass, hybird stripers ect. Bottom line is that a pond can only support a certain poundage of fish and you decide how far you want to spread that out over gills, bass, cats ect. This sit a and other contain incredibly valuable inofrmation about building a good forage base of fish first and then introducing the predator - bass is you choice - allow nature to do its thing augment the feeding with some high protein fish food and hold on.

The third option is what i did and fortunatley it has worked so far. I bought big bass 12 inchers and threw them in 50 largemouth and 50 hybid striped bass and they kicked some gill butt. this option is expensive but has made for some good fishing from the beginning and some expensive purchases of fish chow. goood luck