Many of the native freshwater fish species are not well known to the general public whilst some of the introduced species are so familiar that they are occasionally mistakenly thought to be native to the state. The Tasmanian freshwater fish fauna consists of 25 species of native fish and a further 8 introduced species. At least 15 further species which are predominately marine or estuarine inhabitants, may be found some distance inland at certain times of the year. Some of these are more frequent invaders than others and the listing of species as freshwater is somewhat arbitrary. The lampreys are included in this and other fish guides by tradition, although they are not fishes in the strict sense.