One hundred miles northeast of Boston Harbor, a half dozen endangered sei whales lunge and roll, sleek white bellies flashing in the gray North Atlantic. At the top of each lunge, they throw open tremendous, beaklike maws to strain masses of tiny copepods from the water, which gushes down the sides of their pleated throats. Off the port side of the Plan b, an expedition ship operated by philanthropist Ted Waitt, a school of herring chases the same crustaceans, roiling the surface. Meanwhile, on a rocky ledge 50 feet below, scientists from the ship watch pollacks, cod, and cunners feed among long ribbons of golden kelp.
Cashes Ledge is the highest undersea mountain in the Gulf of Maine—and a remarkable movable feast. As the tides wash over its granite ridges and flat-topped banks, they drive internal waves of warm surface water laden with plankton into the depths. The down-welling waves allow groundfish on the bottom to eat as lustily as fish in the middle of the water and whales, herring, and seabirds at the surface. Tides and topography have conspired here to preserve a vestige of the riches that once defined the Gulf of Maine, until fishing depleted them.
“Cashes is essentially a time machine to the coastal New England of 400 years ago,” says Jon Witman, a trim-bearded Brown University marine ecologist who has studied the hot spot for more than three decades. Oceanographer Sylvia Earle, a National Geographic explorer-in-residence, calls Cashes “the Yellowstone of the North Atlantic”—an American treasure worth saving, even if we can’t go visit in an RV.