Infection with parasites is known to increase with age, but few studies have documented the start point for these infections. Freshwater fish in the Murray Darling Basin (MDB) have been found, through recent research conducted by the Parasitology Laboratory at Charles Sturt University and the Narrandera Fisheries Centre, to be infected with a range of parasites, both endemic and introduced (such as Lernaea and Bothriocephalus). No studies, however, have looked at infection levels in larval or juvenile fish. Collection of larval & juvenile freshwater fish occurs in river systems across the MDB through annual monitoring surveys. After identification to species (primarily Murray cod, carp gudgeons and the introduced European carp), these fish are dissected and examined for parasites to determine levels of parasitism across the fish species. The information collected in this project will have direct benefit to freshwater biologists and fisheries managers. Infections of larval fish with parasites has potential impacts across the entire ecosystem. This will be the first study in Australia to document the level of parasitism in larval and juvenile fish and will provide information regarding the incidence of parasitism across both native and introduced fish.