HomeFish encyclopediaRay-finned fishesPipefishes and SeahorsesPipefishes and seahorsesBastard seahorse Bastard seahorse (Acentronura gracilissima) Scientific name: Acentronura gracilissima Temminck & Schlegel, 1850 The Bastard seahorse (Acentronura gracilissima) is a marine fish of the family Syngnathidae. Native range: Western Pacific, Restricted to areas around Japan and Indochina but there are records from the central and western Indian Ocean. BiologyDorsal soft rays (total): 16. Rings: 13+44-46.Source: FishBase, licensed CC BY-NC 4.0. Species factsScientific nameAcentronura gracilissimaFamilySyngnathidae (Pipefishes and seahorses)OrderSyngnathiformes (Pipefishes and Seahorses)ClassActinopterygii (Ray-finned fishes)EnvironmentMarine; reef-associatedClimateTemperateDistributionWestern Pacific: Restricted to areas around Japan and Indochina but there are records from the central and western Indian Ocean.Conservation status (IUCN)Not EvaluatedThreat to humansHarmlessResilienceHigh, minimum population doubling time less than 15 months (Preliminary K or Fecundity.) SourcesTaxonomy, distribution and biology data: FishBase (Froese, R. and D. Pauly, eds.), licensed CC BY-NC 4.0.Last updated 27 September 2026