With a record low oyster harvest expected, the Maryland Department of Natural Resources is considering shortening the oyster season and imposing new restrictions on the Chesapeake Bay catch.

Officials say they have little time before the scheduled Sept. 15 start of the season to respond to recent surveys that indicate that up to 90 percent of the oysters on some bars in Maryland waters of the bay have died from MSX, or multinucleate sphere unknown.

A DNR committee plans to meet Sept. 8 to decide whether to issue emergency regulations delaying the start of the season, said Pete Jensen, state fisheries director. Other possible harvest restrictions include banning oystering on Saturdays and after 3 p.m. on weekdays, he said.

"We are finding unprecedented levels of mortality as a result of disease all the way up to Kent Island," Jensen told members of the House Environmental Matters Committee Tuesday.

MSX and another disease, Dermo, infected the state's oyster bars in the 1960s and again in the early 1980s, when low rainfall and warm temperatures encouraged their spread up the bay from Virginia into Maryland waters.

The disease has returned this year, scientists said, spreading with the help of drought conditions to new regions of the bay and killing off many oysters before they can grow to harvestable size.

Although fatal to oysters, neither disease has proven harmful to humans who consume shellfish infected by MSX or Dermo.