Importantly, not a single stock that is being monitored has died out, according to the study. Some 19 percent are known to be improving, 5 percent are stable and 5 percent are decreasing.
The Marine Mammal Protection Act actually refocused wildlife officials on entire ecosystems. Because every species -- like the much endangered right whale -- is part of a larger ecosystem, many programs today are broader than a single species. International treaties to protect whales have been credited with curtailing the slaughter of these great animals, and they apply to all whales, with some exceptions.
There is something of an irony over the continuing conflict between humans and some marine mammals, Roman said. Some humans may hate them, because they are perceived to interfere with fishing, and there's no doubt seals and sea lions and the elephant seal can wreak havoc on a beautiful beach. But many people love them.
Whale watching alone brings in nearly $1 billion a year to coastal communities, according to the study.
"In New England, whale watching has arisen in places where fisheries have declined, so it's another opportunity for employment," Roman said. "People pay a fair amount of money to see whales, and even seals and porpoises and dolphins."
Even the stuff they leave behind can be useful, according to Roman.
He and his colleagues have been studying whale pups and "the good news is," he said, the pups dive deep to feed often, and "they are releasing nutrients at the surface in the form of feces. That enhances the growth of algae and seaweed," which increases the organic productivity of the region.
So when the population of marine mammals rebounds, everybody gains, he argues.