The late Steve Irwin’s conservationist father Bob Irwin has urged authorities and the public not to retaliate against crocodiles after a suspected fatal attack on a tourist in Cape York.

Arthur Booker, 62, from Logan, south of Brisbane, has not been seen since he went to check a crabpot at the Endeavour River Escape campsite near Cooktown, north of Cairns, about 8.30am (AEST) on Tuesday.

A crocodile’s track marks were found at the site, but so far, a wristwatch and sandals are the only traces of Booker the search party has found. The Vietnam veteran and his wife Doris were on a two-day holiday at the campsite.

Irwin on Wednesday said the crocodile was just doing what it had to do to survive in the wild.

“I would hate to see this crocodile, or indeed any crocodile, slaughtered because of what happened,” Irwin said.

“The crocodile was simply hunting for food. It’s what they obviously have to do in the wild to survive.

“Because of his reported size, it’s likely that this area of the river would have been his home for at least fifty years.”

Irwin said people needed to be croc savvy in areas like Cape York.

“There are signs all over the area warning locals and tourists that the area is home to saltwater crocodiles,” he said.

“I feel tremendously sorry for the man’s family, and my deepest sympathy goes out to them.

“It is very, very sad for the family. But you really can’t blame the crocodile.”

Swan said 15 people were continuing the search for Booker and would continue on Thursday if nothing eventuated.

“At this stage we’ve got no concrete evidence to support a crocodile was involved but there are crocodiles in that reach of the river,” Swan said.

Mrs Booker has been admitted to Cooktown hospital for observation after being deeply distressed over the incident.

Her sister Carmen Watson has flown to Cooktown, and outside the hospital today urged the media to respect the family’s privacy.

Last night the Endeavour River Escape campsite’s Terry Rayner identified a six metre crocodile named Charlie as the key suspect.

“He lives there. That’s his territory. He’s the alpha male there,” Rayner said.

But Queensland Parks and Wildlife Service regional manager James Newman today told ABC Radio that two other large crocodiles were spotted in the area and search crews were exercising caution.

“They will be looking in the water today and having a look at the bottom to see if they can’t pull anything off the bottom,” Newman said.

The University of Queensland’s crocodile expert Professor Craig Franklin said crocodiles were ambush predators on the lookout for repeated patterns of activity from potential prey.

“They don’t target humans. They’re opportunistic feeders,” Franklin said.

“If a food source presents itself then they see that as fair game.”