The man was night fishing on Saturday at Peter Faust Dam, 26km inland from Proserpine in the Whitsunday region, when he spotted the scaly predator.

"He saw what he thought was a crocodile's eyes shining and moved his boat closer," a Department of Environment and Science spokesman said on Thursday.

After confirming it was a crocodile, the man captured the reptile then took it home.

He later alerted wildlife officers, who are now investigating the circumstances surrounding the catch.

"Our main concern about this is we don't want people taking matters into their own hands when they see an estuarine crocodile," wildlife operations director Lindsay Delzoppo said.

"If people do try to interfere with a crocodile like (allegedly) appears to have happened, they place themselves in grave danger of being attacked or harmed.

"An animal of that size could do great damage to someone's arm or leg."

Rangers later took the 1.7 metre crocodile to a zoo.

Mr Delzoppo reminded the public that it's an offence to deliberately interfere with, harm or kill a crocodile, carrying a maximum penalty of $30,026.

Saltwater or estuarine crocodiles can be found in a wide range of habitats, including rivers, estuaries, creeks, swamps, lagoons and billabongs.

They can tolerate freshwater to full-strength seawater, and have even been recorded in water twice as saline as the ocean.

Physical barriers such as escarpments and other types of rapidly rising ground generally limit the animal's upstream movement.

Australian Associated Press