Short-finned Eels (the dark ones you catch in rivers, lakes, dams, the Melbourne Botanic Gardens etc) breed in the ocean, and yes, as I said in my last post, they migrate up to several kms over land. The Yarra is right near the Botanic Gardens, so it's a very easy place for them to reach. Baby eels are called elvers, they get into fresh water bodies or stay in rivers, grow up, then go back to the ocean to breed. Sometimes lost adult eels turn up in strange places. Once in a blue moon we had them turn up at my primary school, much to the confusion and amusement of some of us!