 Many tawny nurse sharks found off the coasts of Japan , Taiwan , and the <unk> Islands lack a second dorsal fin . This physical <unk> has been speculated to result from pregnant females being exposed to water of unusually high salinity and / or temperature , possibly from human activity . In 1986 , a 2 @.@ 9 m ( 9 ft 6 in ) long adult male with both a missing dorsal fin and partial albinism ( in the form of white body color with gray @-@ brown eyes ) was captured off <unk> Prefecture , Japan . This <unk> individual is the largest <unk> shark known to date , having survived for a long time in the wild despite its lack of camouflage . 
