TALLAHASSEE, Fla. (AP) _ Hurricane Kate wiped out nearly half of rich Apalachicola Bay's oysters, most of them young spats formed after Hurricane Elena and important to the bay's recovery, a study said Friday.

The study differed from official state estimates earlier this month that Kate's damage was much lighter than first feared.

Overall, Elena wiped out 77 percent of the bay's crop, and Kate killed 40 percent to 45 percent of the remaining oysters, many of them spats, said the study by Robert J. Livingston, director of Florida State University's Center for Aquatic Research and Resource Management.

Apalachicola Bay supplies more than 90 percent of Florida's oyster production and nearly 8 percent of the nation's.

The bay, which has been closed to oystering since Hurricane Elena struck Sept. 1, produced $4.7 million worth of oysters alone in 1983, according to the latest Department of Natural Resources figures.

After Elena swept across the bay in late August and early September, the bay was in the height of its spawning season and was recovering. But Kate brought 100 mph winds to the most productive oyster beds, the report said.

With the spawning season over and no chance for immediate recovery from Kate, the bay will take longer to return to its former abundance, Livingston said. He did not say how much longer.

Charlie Futch, assistant director of the state Division of Marine Resources, said earlier this month that the bay would be back up to production within a year to 15 months from when Elena swept through. Futch did not return a call to his office Friday for comment on Livingston's study.

Livingston called for a sound management plan to make sure the bay has a chance to regenerate.