WASHINGTON — The National Oceanic and Atmospheric Administration greatly expanded the fishing ban in the Gulf of Mexico on Tuesday in response to spreading oil from the BP well blowout. The prohibited area now covers 19 percent of the gulf, nearly double what it was, according to the agency.

Officials are already seeing some impact on fish and wildlife in the region. Rowan W. Gould, the acting director of the Fish and Wildlife Service, said 156 sea turtle fatalities had been recorded in the gulf since April 30, about 100 more than usual at this time of year.

Mr. Gould also said that a small number of oily birds, 35, had been recovered, including 23 dead birds directly linked to the spill.

“It’s important to note that the visibly oiled birds are a small part” of the effects of the oil spill, Dr. Gould said in a teleconference on Tuesday.