RANGERS spent five hours combing the Burnett River after receiving an alarming report of a rogue crocodile, only for the likely culprit to be a very large fish.
Department of Environment and Science staff carried out a spotlight patrol around the Sandy Hook area of the river on Tuesday night and found no signs of any crocodiles.
DES Conservation and Biodiversity Operations acting director Frank Mills said at this stage, wildlife officers believed the reported sightings were more likely of very large lungfish.
"After discussions with locals and our own observations, it is most likely the observers saw either one or a number of very large lungfish, which are native to the area and can grow up to two metres in length," he said.
"The behaviour described to us of the animals seen in the area is inconsistent with typical crocodile behaviour, however, it does match up with lungfish behaviour.
"Our observations indicate a healthy lungfish population in the area, which is good news in terms of conservation."
Wildlife officers returned to the scene of the sightings yesterday and last night to continue the search for the reported croc.
"DES takes all crocodile sighting reports seriously," Mr Mills said.
"Although we didn't find any indication of recent croc activity last night, we will continue to search the area thoroughly as part of our investigation.
"We encourage all members of the public to report crocodile sightings to the department by calling 1300 130 372."
The Australian lungfish is native to southeast Queensland and often found around the Wide-Bay/Burnett area.
The species is called a lungfish because of its ability to breathe air using a "lung", although they also have five sets of gills.
The lungfish is the only Australian survivor of a species of fish that has been around since the time of the dinosaurs and relies on healthy wetlands to survive.