They followed the trail as far as they could, but it ended, probably because of hard packed ice.
However, it meant they now had a last known point from which to start searching, Watson said.
This morning land-based search and rescue teams, including specialist dogs, were sent into the area.
The NZCC West Coast Rescue Helicopter was helping move teams, but its role in searching was largely over, as they were looking at bush areas.
Watson said the Paparoa Range tops had snow and the conditions there were "freezing". The past two nights had been clear and frosty.
Heat-seeking equipment was used for two or three hours last night, but with no result.
Watson said the missing man was dressed only for a day tramp, and was not carrying a locator beacon.
Police now have serious concerns for his safety.
Area commander Inspector Mel Aitken said committed ground teams with a huge amount of expertise were involved in the search. Fifteen ground searchers were out today.
"Our thoughts are with the family at this time, as we continue our best efforts to reach a positive conclusion to this rescue," Aitken said.
Experienced Barrytown tramper Stewart Robertson said the Mount Bovis walk was a 10km round trip, involving a 3500ft ascent.
There is no track and trampers have to find their way by markers.
"Cyclone Ita has knocked over lots of trees on the route. Locals have re-marked with dazzle paint spots and pink tape, but there is still ample scope to wander off-route, especially on the descent," Robertson said.
"The cyclone damage calls for a lot of ducking and diving around fallen trees so now takes longer than expected."
Robertson said he had walked up Mount Bovis eight times, once since the cyclone.
"At the best of times, route finding is challenging and on the tops, an extra challenge in mist."