Selling means commercial and you must follow commercial regs.
If you find someone to unload a few fish on under the table I say go for it..
"Commercial Fishery Regulations
Both the recreational and commercial fisheries for bluefin tuna are regulated by the National Marine Fisheries Service."
http://www.mass.gov/dfwele/dmf/recre...luefintuna.htm
"All persons who land and sell finfish, shellfish, lobsters, edible crabs or other living marine resources in Massachusetts must have a commercial fishing permit from the Division of Marine Fisheries and must sell only to permitted Massachusetts dealers. "
Mass. Division of Marine Fisheries - Permits