SAVANNAH, Ga. — Scientists say only six endangered right whales were born this past winter in the calving grounds off the coast of Georgia and northern Florida.

But there is good news despite the poor season: None of the whales were killed by ships in the critical habitat area.

The most threatened species among large whales, with a population estimated at just 350, the right whale travels each winter to the warm, shallow coastal Atlantic waters — its only known calving grounds.

In the winter of 1996-97, 17 calves were born in the designated critical habitat area, which stretches from just north of the St. Marys River to Cape Canaveral.

Of the six documented calves born this year, one was a stillbirth, said Chris Slay, a researcher at Boston’s New England Aquarium.

Each winter, Slay and a handful of other researchers migrate to Fernandina Beach, Fla., to track the whales for the National Marine Fisheries Service and the states of Georgia and Florida.

In the summer, both the researchers and the whales return to the Bay of Fundy in eastern Canada.

The mammals are so rare that researchers like Slay know most of them by sight. In a good year, such as the productive 1996-97 calving season, the population might grow by 4 to 8 percent, Slay said.

The scientists say this past winter, El Nino-induced weather patterns made for rough seas and stormy weather.

Since the last big El Nino in 1983-84, Robert Kenney, a professor of oceanography at the University of Rhode Island, has tracked right whale births and the atmospheric pressure of the Southern Oscillation Index — an El Nino-related event in the Atlantic.

Kenney has found a parallel between the pressure index and right whale births in the following year. When the average pressure index for a given year drops, as in the case from October 1996 to September 1997, the following year has a lower than average right whale birth rate, Kenney said.

One possible connection is that El Ninos disrupt deep ocean currents, scattering the concentration of copepods — tiny sea creatures the whales feed on. Mother whales may not have enough food to carry their one-ton babies to term, or may tend to have stillbirths.

Another possibility is that the disrupted currents may make it harder for the few remaining right whales to find each other. Instead of spending energy finding mates and mating, whales are searching for food.

Slay and Kenney still have hope for this year’s whale crop. It’s not unusual for mother whales to appear in the Bay of Fundy in the summer with calves that researchers have not spotted before — born nobody knows where. No one knows the exact migration patterns of the right whales between the winters off Florida and the summers off Canada.

Still, researchers agree the 1998-99 calving season will be critical to the right whales’ survival. Two low-birth years in a row could be disastrous.

Despite the low birth rate this year, an effort to protect the right whales appears to be working.

A key is an elaborate communications network funded in part by the U.S. Navy that alerts ships when a right whale is spotted. The mammal’s location is transmitted to each commercial and military ship as well as dredges from Miami to Brunswick — all within about three minutes of the whale being spotted. Ships then turn and slow to avoid the whales.

Collisions with ships are the biggest known cause of death for adult right whales. The slow, shallow-diving whales do not seem to hear the sound frequencies ships make when approaching and do not get out of the way.

“The early warning system is working,” said Cyndi Thomas of the Florida Department of Environmental Protection.