The shooting death of a 4.3 metre crocodile that was found washed up on a riverbank in far north Queensland is being investigated by the Environment Department.

A photo posted on social media appears to show a man standing next to the monster crocodile on the banks of the South Johnstone River at a farm at Wangan, south of Innisfail.

The man is not believed to have anything to do with the crocodile's death, and the photo has since been deleted.

A Queensland Department of Environment and Science (DES) spokeswoman said the crocodile was shot last month and rangers were called to recover the carcass.

Crocodiles are a protected species in Queensland, with the illegal taking of a crocodile in the state carrying a maximum fine of $28,383.

Earlier this year farmer Errol Copley, 69, was fined $500 in a far north Queensland court after he trapped a 3 metre crocodile at his property at Deeral, south of Cairns.

The crocodile had drowned, and its carcass was discovered attached to the trap by Queensland Boating and Fisheries Patrol officers on January 18.

DES set up surveillance cameras in the area, which captured Mr Copley removing the carcass from the trap.

Police have since appealed against the court-imposed penalty, arguing Copley's $500 fine with no conviction recorded would not deter farmers from killing crocodiles.

The Katter's Australian Party (KAP) has introduced a bill to set up a new Queensland crocodile authority that could cull the reptiles.

A parliamentary committee is due to report on the bill by late September.

Queensland KAP MP Shane Knuth, whose electorate covers the area, said residents were becoming fed-up with the "explosion" in crocodile numbers and were taking matters into their own hands.

"The bill is designed to take back our populated waterways from the threat of crocodiles, particularly in north Queensland," he said.

The DES has appealing for anyone with information about the latest crocodile killing to contact them on 1300 130 372.

In April, the Queensland Government said the culling of any problem crocodiles was not a solution and would give the public a false sense of safety.

The State Government is conducting a three-year survey of crocodile numbers in north Queensland.

So far, more than 1,200 kilometres of waterways have been surveyed since the project began in 2017.

The Government said data from surveys would be released when the monitoring program had been completed and results properly analysed.