You don't need a permit.
http://www.mass.gov/dfwele/dmf/recre.../rec_index.htm
Note: A person may, without a special permit, use a small net of no more than 200 square feet inside those inshore waters listed in 322 CMR 4.02(2) or inside any estuary, embayment, salt pond, tidal creek, river, or an other similar body of inshore water for the sole purpose of obtaining bait fish for personal use.
The area of a 8 foot net is just about 200 square feet.
I think you need a bait license to use a bigger net but I've never seen anyone measuring.