A member of the public found a dead platypus in abandoned hoop nets in the Yarra River at Warburton East on Tuesday 13 May.
The Conservation Regulator Victoria is seeking information from the public to investigate this incident.
Penalties can apply for abandoning nets and traps.
Anyone with information about this incident or other wildlife crimes can make an anonymous report online at: crimestoppersvic.com.au or call on: 1800 333 000.
Illegal or abandoned nets and traps in waterways are a threat to native wildlife including turtles, platypus and rakali.
In Victoria it is illegal to use certain types of fishing equipment in public waterways.
