US government researchers have spotted 44 right whales in the Gulf of Maine last week, perhaps evidence of a new breeding ground for the endangered species.

The aerial survey may help in coordinating efforts to protect the whales, hunted nearly into extinction in the past two centuries, the researchers at the National Oceanic and Atmospheric Administration said.

"We're excited because seeing 44 right whales together in the Gulf of Maine is a record for the winter months, when daily observations of three or five animals are much more common," said Tim Cole, who heads the team at NOAA's Northeast Fisheries Science Centre.

"Right whales are baleen whales, and in the winter spend a lot of time diving for food deep in the water column. Seeing so many of them at the surface when we are flying over an area is a bit of luck."

Baleen whales use their huge mouths to filter small plants and creatures for food out of the water.

Many female North Atlantic right whales head south to Florida and Georgia to give birth in the winter, NOAA said in a statement. But scientists know little about where other right whales go in winter.

Only 325 of the giant mammals are known to survive.

"Because only about 100 right whales, mostly females and their calves, are sighted each year in aerial surveys off the southeast coast, we know the remainder of the population must be somewhere else. We don't know much about where these other whales spend the winter or breed, but we have recently started to look in the Gulf of Maine in winter," NOAA'S Pete Duley said in a statement.

The world imposed a moratorium on all whale hunts in 1986 after many species were driven toward extinction by decades of exploitation for meat, oil and whalebone. Japan, Norway and Iceland still hunt minke whales, arguing they are plentiful. Boats and fishing lines still pose a big danger for the animals and the US government has put into effect new speed rules for large ships to help them avoid injuring whales, especially right whales.