HomeFish encyclopediaRay-finned fishesBony tonguesMooneyesMooneye Mooneye (Hiodon tergisus) Scientific name: Hiodon tergisus Lesueur, 1818 The Mooneye (Hiodon tergisus) is a freshwater fish of the family Hiodontidae. BiologyOccur in deep pools and backwaters of medium to large rivers, lakes and impoundments.Source: FishBase, licensed CC BY-NC 4.0. Species factsScientific nameHiodon tergisusFamilyHiodontidae (Mooneyes)OrderOsteoglossiformes (Bony tongues)ClassActinopterygii (Ray-finned fishes)Maximum length47.0Common length28.3EnvironmentFreshwater; pelagicClimateTemperateDistributionNorth America: St. Lawrence-Great Lakes in Canada-USA, Mississippi River in USA, and Hudson Bay basins from Quebec to Alberta in Canada and south to Gulf of Mexico; Gulf Slope drainages from Mobile Bay in Alabama to Lake Pontchartrain in Louisiana, USA.Conservation status (IUCN)Not EvaluatedThreat to humansHarmlessResilienceMedium, minimum population doubling time 1.4 - 4.4 years (tmax=10) SourcesTaxonomy, distribution and biology data: FishBase (Froese, R. and D. Pauly, eds.), licensed CC BY-NC 4.0.Last updated 27 September 2026