I work at Gander Mountain and in the summer we have them at about 60 degrees, but in the winter we keep them right around 42. In lower temperatures Oxygen doesn't deplete as fast, their metabolism also slows down, and another factor is if you're using them for ice fishing and if you drop them into frigid 33 degree water, after coming out of water that is high 50's, they may die from shock. I guess if they are in your bucket and in the cold for awhile the water will gradually get cold and it wouldn't be as harsh because the change is gradual. Just some of my thoughts...
Also, I'm not sure what the regs are in Mass, but here in New York we can only keep them for 10 days. Good luck!