YARMOUTH, Mass.  Dave Lamoureux’s kayak, named Fortitude, must be the only one in Massachusetts registered as a motor vessel. That’s because a powerboat registration is required to get a permit to fish for tuna here.

Apparently, it never occurred to the authorities that someone might be crazy enough to want to catch a bluefin while sitting in what amounts to a floating plastic chair and enjoying what Melville called a “Nantucket sleigh ride.”

Since the end of July, Lamoureux has caught three bluefins this way, paddling a couple of miles off Race Point, at the tip of Provincetown, hooking a tuna and holding on, the rod clipped to a harness on his chest, while being towed at speeds up to 15 miles an hour before the fish exhausts itself.

His most recent catch, on Nov. 5, was a 157-pound bluefin, a record tuna for an unassisted kayak fisherman, and a near record over all, topped only by a 183-pound halibut caught by Howard McKim, an Alaskan, in 2004. Reeling in a halibut, though, has been likened to hauling in a load of plywood, and some of Lamoureux’s admirers consider landing a bluefin, known for its power and ferocity, the greater feat. He is a hero at bait shops up and down Cape Cod. On fishing blogs, a few grumblers call him a dangerous idiot.