Slender Rainbowfish is endemic to Australia. The species occurs in a restricted distribution area in the Kimberley region, northern Western Australia where it is found in the Drysdale River and the King Edward River systems. Within its restricted range the species is locally abundant.
In 2019 the Slender Rainbowfish was assessed as Endangered because its limited distribution and continued threats that affect the species habitat. The population is currently stable.
■ Included in the IUCN Red List of Threatened Species in 1994, listed as Endangered (EN) since 2019.
■ Phylum Chordata – chordates
■ Class Actinopterygii – ray-finned fishes
■ Order Atheriniformes – silversides
■ Family Melanotaeniidae – rainbowfishes
■ Species Melanotaenia gracilis – Slender Rainbowfish