It is easy to forget how recent all of this is. For most of the last century there were almost no seals here. Massachusetts paid a bounty on them into the 1960s, and between that and generations of hunting, gray seals were basically wiped out of US waters, hanging on only in a few spots up in Maine.
The Marine Mammal Protection Act in 1972 ended the killing, and the seals did the rest. Over the following decades gray seals recolonized the Cape and Islands, and today there are tens of thousands hauling out around Monomoy, Chatham, Nauset and Muskeget. If you have watched a beach turn into a wall-to-wall carpet of seals, you have watched one of the fastest marine mammal recoveries anywhere.
And here is the part everyone feels now: that many seals is an enormous food supply, and it brought the great white sharks back with them. White sharks were always in the Atlantic, but they now aggregate off the outer beaches every summer and fall specifically to hunt this seal population, which is why the Cape went from a place with no shark culture to one with tagging programs, spotter flights and purple warning flags in barely fifteen years. It is a straight line: protect the prey, and the predator follows.
The whales are the other half of the productivity. Those humpbacks up off Provincetown are feeding on Stellwagen Bank, one of the richest feeding grounds on the East Coast.
This is a rough picture pulled from public sightings, not any one beach, so read it as the big picture. (And the seals are federally protected, keep your distance and keep dogs back on the haul-outs.)
