That's nutty. Whales have been thriving in the sea for millions of years. They achieve, like all creatures, a balance with their source of food. It's only when people came along fishing with advanced technology that the fish population collapsed (cod is practically extinct in many former fishing grounds). And no fish means starving whales.

So it's greedy people who are hoovering up the fish faster than they can breed, not whales.

And we will achieve a balance with our food supplies eventually. The process will probably not be very pleasant.