Killer whales in the Olympic Coast National Marine Sanctuary. (Photo Credit: NOAA)
Marine Mammal Protection Act proves effective
Monday, May 06, 2013, 03:00 (GMT + 9)
In 1972, a US Senate committee reported, "Many of the great whales which once populated the oceans have now dwindled to the edge of extinction," due to commercial hunting. The committee also worried about how tuna fishing was accidentally killing thousands of dolphins, trapped in fishing gear. And they considered reports about seal hunting and the decline of other mammals, including sea otters and walruses.
In October of that year, Congress passed the Marine Mammal Protection Act and four decades later, new research shows that the law is working.
Not only has the act "successfully prevented the extirpation of any marine mammal population in the US in the 40 years since it was enacted," write University of Vermont conservation biologist Joe Roman and his colleagues in a new report, but also, "the current status of many marine mammal populations is considerably better than in 1972."
Their study, published online in the Annals of the New York Academy of Sciences, shows that population trends for most stocks of these animals remain unknown, but of those stocks that are known, many are increasing.
Some marine mammals, like endangered right whales, continue to be in deep trouble, but other populations "particularly seals and sea lions, have recovered to or near their carrying capacity," the scientists write.
"We have seen remarkable recoveries of some populations of marine mammals, such as gray seals in New England and sea lions and elephant seals along the Pacific coast," says Read.
"US waters are pretty compromised with lots of ship traffic and ship strikes, big fisheries, pollution, boat noise, " Joe Roman says. "And yet it's safer to be a marine mammal in US waters than elsewhere," he says, due to the Act's strong protections against commercial and accidental killing — what the law calls "take" — and its aim to maintain sustainable populations of mammals and their ecological roles in oceans.
"It's important to evaluate such broad legislation," says co-author Caitlin Campbell, a UVM student.
"A lot of people think that the hard part was getting it passed through Congress, but in reality you have to make sure that big protective measures like this are actually effective," she says. "This paper shows that this act is doing its job."
The research team gathered hundreds of data sets from around the world, including from the National Oceanic and Atmospheric Administration (NOAA), Canadian agencies, and the International Union for Conservation of Nature and Natural Resources (IUCN). Their goal was to get an accurate picture of population levels and trends of more than 200 stocks of marine mammals from the Pantropical Spotted Dolphin to the West Indian Manatee.
The team concluded that for many of these animals there simply aren't enough data. For 71 per cent of the stocks they identified, they couldn't say which way the population was heading, up or down.
But for the ones they could evaluate, they found that 19 per cent of stocks were increasing, while five percent were stable and only 5 per cent were declining.
Another fundamental conclusion of this research: "stopping harvesting these mammals, stop fisheries bycatch, stop killing them — and many populations bounce back," says Roman. Marine mammals are long-lived "so it's going to take decades, maybe longer for populations to rebound," he says, "but it seems the trends are increasing."