Guyu wujalwujalensis, the tropical nightfish or Bloomfield River cod, is a species of temperate perch endemic to Australia. It is only found in an 11-km stretch of the Bloomfield River (between two large waterfalls) in northern Queensland. These waterfalls appear to have blocked the migration of more aggressive tropical freshwater fish species such as the sooty grunter (Hephaestus fuliginosus) that have presumably naturally displaced the Bloomfield River cod from its former range in prehistoric times. With its very limited distribution, the Bloomfield River cod is clearly a relict species. It is a very important relict species, however, as it is the most northerly distributed percichthyid species in Australia, and raises interesting questions on the biogeography of percichthyid fish in Aus