I'm not sure if drawing down would work but since someone told you they were surprised they were surviving the winter the idea came to mind. I'm no expert but I'd guess it would depend on how deep the pond is and how much water is flowing through.
http://blog.mlive.com/chronicle/2008/04/dnr_official_lake_fish_kill_li.html

A drawdown would also decrease shorline vegetation. There was a good article in PB magazine about this recently.

I think I read somewhere that HSB were not legal to stock in MI, but are pure blood stripers? Either are effective predators of the shad if legal. I have gizzard shad in my pond and they quickly grew to 15" or 16" but have been kept in check by HSB.



"The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge." Stephen W. Hawking