What if your pet fish could wreak havoc on Australia’s ecosystems? Turns out, that’s precisely what they’ll do if they end up in our waterways.

In today’s episode, Dr. Siwan Lovett sits down with freshwater fish biologist Dr Mariah Millington, who reveals the surprising capacity for non-native pet fish to damage and degrade Australia’s freshwater ecosystems, and particularly the native fish that live within them. Discover how to best dispose of dead pet fish, how common goldfish and other popular pet species can grow to alarming sizes and cause severe ecological damage when released, Mariah’s undercover research into forums and marketplaces on the Deep web, and some of the specific species which pose significant ecological risks to Australian native fish, whose populations are already estimated to be less than 10% of their pre-colonisation numbers.

Mariah pulls back the curtain on the underground world of illegal fish trade and the challenges in regulating this thriving online market. You’ll be intrigued by the prevalence of pet fish in Australian households and the secretive subculture of basement breeders who bypass legal regulations through platforms like Facebook and Gumtree. From the complexities of transporting fish over long distances to the hidden layers of the web where these transactions occur, our conversation uncovers the dark side of the pet fish industry and the ecological risks it poses.

The threats don’t stop there—Tilapia and other invasive fish species are making alarming inroads into Australia’s waterways. Tilapia in particular continue to head further south. Learn about the reproductive strategies that make tilapia particularly dangerous and the potential for hybridization to increase their invasive potential. Mariah discusses the importance of public education, biosecurity measures, and promoting native fish conservation initiatives.

This episode is a compelling call to action for protecting our native fish populations and the ecosystems they depend on.