NZ has never been covered entirely since it first arose. That said, all of our endemic fish are either amphidromous (can live in fresh or salt water, bullies,

NZ has never been covered entirely since it first arose. That said, all of our endemic fish are either amphidromous (can live in fresh or salt water, bullies, and the larval phases of most galaxiids) or if not, most likely descended from other galaxiids that were - e.g., the alpine galaxias. Galaxiids are found in Australia and South Africa also. https://niwa.co.nz/freshwater-and-estuaries/nzffd/NIWA-fish-atlas/fish-species/galaxiidae https://niwa.co.nz/freshwater-and-estuaries/nzffd/NIWA-fish-... > It is thought that the non-diadromous species of Galaxiidae have evolved from the diadromous species, probably after geological events caused them to become land-locked. Gradually, these species have developed separate populations and distinguishing characteristics.