Congregations of whales usually indicate parts of the ocean that are especially productive. There has to be a dense concentration of prey to support that many humpbacks. And yes, the word "prey" might sound strange for a species known for singing songs and being friendly to other mammals. Lest we forget, humpback whales do hunt for their food. They're not vegetarians. They eat everything from krill to plankton to small fish, regardless of whether they speak whale. They even have a specialized way of hunting where they gang up on schools of fish to try to eat them all at once. It's called bubble net feeding. The humpbacks divide up, some swirling around a group of fish and some blowing air, such that the circling whales can drive their victims into a net made of bubbles. This confuses the fish, trapping them inside, until one whale sounds the call and they all rush in, mouths agape, swimming upwards through the teeming mass of fish.