Footprints of a tramper missing in Mount Aspiring National Park have been found going into a river, but not coming out.

The man was walking with his partner and her family on Sunday evening, when he chose to traverse a difficult gorge near the Wilkin River, rather than follow the track.

Wanaka Search and Rescue spokesman Phil Melkeyor says rescuers have their fingers crossed they can find something at the river today.

"Obviously the longer this goes on, the more concern there is and the less hopeful we're going to be."