Simplify the following text for a Grade 7 native English-speaking person.
Original: By Secretary 's Order No. 3210 of December 3 , 1999 , the United States Fish and Wildlife Service assumed administrative responsibility for Navassa , which became a National Wildlife Refuge Overlay , also known as Navassa Island National Wildlife Refuge .
Simplified: On September 2 , 1999 , the U.S. Fish and Wildlife Service established the Navassa Island Wildlife Refuge as an overlay .