I grew up in the South Hadley area and spent MANY days targeting shad before the bass took over my mind. Landed American shod to over 7 pounds back when I was younger, just never on the derby weekend. The area from the Holyoke dam to about 3/4 mile south is about as prime as you can get. Basically just find some river access and follow the crowds. I used to hang with the Worcester guys when they would come up for the weekend and had a blast. If you are familiar with Delaware river fishing, you should be able to figure out the CT river pretty easily. I would be willing to share some of my experiences and spots if you want to drop me a PM. It is a solid 2 hour ride from the canal, though.
The Chicopee and Westfield rivers also have some very good runs. I landed my one and only Atlantic salmon in the Westfield around '95 or so. Awesome battle on a 5 weight fly rod and reel with no drag.

We used to drift rubber salmon eggs on the fly set up for shad there. Had a spot where you would stand on a rock and site fish the pool below. I tormented that salmon for a good 30 minutes before it got mad and ate my offering.