Genetically unique fish found in waters of Lord Howe Island Marine Park

Lord Howe Island Marine Park staff recently observed an unusually coloured Doubleheader Wrasse (Coris bulbifrons) in the waters of the Lord Howe Island lagoon.

This species is the largest of the genus Coris and is endemic to the waters surrounding Lord Howe Island and Norfolk Island. Adults are usually a steel blue colour, with males having a distinctive hump on their heads.

However, the unusual adult male observed had pied colouration, with blotches of steel blue on an otherwise white body.

Advice was sought from a fish ecologist and geneticist with experience in island-endemic species, who suggested a probable cause of this discolouration is a recessive genetic trait. Inbreeding is more likely in small, isolated fish populations such as the endemic Doubleheader Wrasse, which can result in rare recessive traits being combined during spawning and ‘expressed’ in the resulting offspring.

Another example of a recessive trait seen in a Lord Howe Island Marine Park fish population is the distinctive ‘golden drummer’.

Many Lord Howe Island residents and visitors will have seen a school of silver Pacific Drummer (Kyphosus sectatrix) with a single bright yellow individual among them.

This colouration is called ‘xanthism’ and although Pacific Drummers occur on warm tropical reefs worldwide, this phenomenon seems to only occur in small, isolated populations around oceanic islands due to inbreeding.

Thanks to Dr. JP Hobbs for providing advice on these phenomena.