SAVANNAH, Ga. (AP) — Scientists have yet to spot a single newborn right whale off the Southeast U.S. coast seven weeks into the endangered species' calving season.

It's the longest researchers have gone without a calf sighting since comprehensive surveys started in 1989.

Scientists say only about 450 North American right whales remain. They typically migrate to waters off Georgia and Florida to give birth between December and April.

Clay George is a biologist who monitors right whales for the Georgia Department of Natural Resources. He says he's concerned because mid-January is typically the peak of the calving season. Five births recorded last year were the lowest since 2000.

It's possible bad weather is to blame rather than a reproductive slump. Windy, cloudy conditions have frequently kept planes from searching for whales this season