Our understanding of the bluefin is still limited. We know there is some east-west mix in Atlantic stocks, but we don't know how much or why. If you want to learn more about them, I recommend following Molly Lutcavage, the director of the University of Massachusetts Large Pelagics Research Lab in Gloucester, Massachusetts, who is one of the world's foremost tuna researchers. She and her colleagues exploited decades of tagging research to find a bluefin spawning area on the East Coast, which could explain several scientific puzzles.
While I admire their strength and mystery, I must admit that there is nothing quite like a bluefin tuna steak. It's a fish that eats like the greatest steak I've ever had.