The McCann family is appealing to hunters traveling in the backcountry west of Edmonton to keep their eyes open for any clues that might help police locate Lyle and Marie McCann.
"We appeal to these hunters, landowners and others to keep an eye out for anything unusual or out of the ordinary," said Brett McCann.
"What may seem insignificant to you may mean the world to us."
Lyle, 78, and his wife, Marie, 77, went missing on July 3, 2010 after leaving St. Albert, Alta., bound for British Columbia.
Their motorhome was found southeast of Edson, Alta., completely destroyed by fire.
Despite hundreds of tips, numerous ground searches and pleas to the public, police have been unable to discover what happened to the couple.
This hunting season Alberta Sustainable Resource Development is distributing leaflets to stores in the Edson-Evansburg area that sell hunting licenses, asking they be handed out with each permit sold.
"There's a vast area of bush out here that hunters may be travelling in," said McCann. "A hunter may be going in an area that hasn't been entered for years."
Potentially thousands of people comb the area during hunting season, said Brian Voogd, Edson district fish and wildlife officer.
"We ask them to keep vigilant."