I have a distant relation in Vermont who has monster trout in a very similiar size pond with lots of cool fresh water running through. It is strictly a family catch and release pond. But the brookies and browns did very well.
Maybe you can talk the state into giving you one of the big cow trout or salmon that are being put out to pasture.
Theres fish farms where you can order sunfish, carp, trout, stripers and hybrids, etc. Just do a search on google, im sure they could give you all the advice you need too.
Mike is it on your property? If so I'd check with the Mass. Dept of fish and game. Not worth getting in trouble over. Then maybe Largemouth, Red perch and some form of shiner or chub.