Freshwater fish as hosts for parasites in Australia: How much do we really know?

Australia has a highly endemic freshwater fish fauna, but basic biological knowledge for most is lacking. This includes an understanding, and description, of their parasite fauna. Additionally, the impacts of introduced fish species, and their parasites which have transferred across to native species, are also mostly unknown. This review provides the current level of knowledge of parasitic infection of the freshwater fish in Australia, both introduced and native. Only about a third of the native freshwater fish, but almost two-thirds of introduced fish, have been reported as a host for a parasite. The majority of records occur along the eastern coastline of Australia and throughout the Murray Darling Basin; two drainage regions were yet to record any parasite infections. Of the 124 fish species, across 43 families, found as hosts in Australia, only 11 species had more than 10 reports of infection, with 31% of fish species only having single reports. A total of 13 different types of parasites were reported, with digeneans, protozoans, nematodes and monogeneans the most commonly reported. Significant gaps in the knowledge of parasites, and their potential impacts, of Australian freshwater fish still exist, and the need for fish biologists and fish parasitologists to work together is highlighted to ensure that as much information about each group can be obtained.