As far as I know they don't stock the Blackstone in Mass, they do in Lincoln and Cumberland RI though.
In mass they do stock Lake Quinsigamond, the Mumford river and West river as well as a few other locations that are either tributaries or could easily spill into the Blackstone, especially during high running or flood stages. If your truly interested in some sport try fly fishing carp along the Blackstone, with an immense strength and weights well into the 20's possible it can be a blast, and a good gear check
On a side note, fishing without a license robs every angler as well as the Wildlife departments of needed resources to maintain fisheries. It saddens me when people feel they can and/or should fish illegally
. As a fellow fisherman I ask that you please fish responsibly.