Well, if it wasn't a basker it could very well have been a mako. Anyone {who knows}knows the biggest makos in the world are seen/ caught on stellwagen.
There was a 1,500 pounder fought on a 130 bent butt a while back, This one here on the forklift from nova scotia is a beast. and this est. 1,700 pounder was also caught on stellwagen.
SOoooo. If indeed the fish spoted here wasn't a basker, I personally have never seen a mako anywhere near this size. I did see Damon Saco's tiger up close and could see how you {or I} could give or take a few feet.
Tuna/ bluefish grabs the jig, Shark grabs the fish and off we go...

Huge Mako would be believable.
They jump.
They are big.
They would hit a jig.
They are on stellwagen.
