AT THE BOATYARD BEFORE dawn on a morning in early January, Tsunehiro Kawahara was waiting for me. We braced ourselves and walked down the frosty gangway, its metal railing too cold to grasp. We greeted Kenrou Kawasaki, a rugged aquafarmer, and boarded his 12-meter vessel. He invited us into the small heated cabin, took his seat at the helm, and maneuver…