Katherine-based Parks and Wildlife Commission NT rangers swung into action on Thursday morning to check out what was in the trap, with several crossing their fingers that they had finally caught a saltwater crocodile as it made its way upstream.

The last saltwater crocodile trapped in the town reach of the river was in October 1999 and senior ranger John Burke said it was not known why only freshwater crocodiles had found their way into traps in the vicinity of the High Level Bridge during the past 15 years.

“The portion from High Level to Low Level has the highest population density of freshwater crocodiles in the Katherine River,” he explained.

“Two freshwater crocodiles do live in that area [around the trap], however, we have had reports of a ‘large croc’ hanging around the bridge, species unknown.”

Mr Burke said it was possible people had mistaken freshwater crocodiles around the High Level Bridge for their saltwater cousins because of their size.

“Many people are not aware that freshwater crocodiles can grow over 3m in length and, as a result, are surprised when they are shown one of significant size,” he told the Katherine Times.

“I would expect that most people normally only get a glimpse of a large crocodile entering the water and would not see the head, which assists in identification.

“We encourage members of the public to report all sightings of salties and crocodiles they are unsure of.”