Clutha flathead galaxias Galaxias ‘species D’
The Clutha flathead galaxias (commonly known as the Clutha flathead) is one of Otago’s more peculiar galaxiid species as between individuals, this galaxiid can not only look very different, but be genetically different also. Classified as ‘Nationally Critical’ it is one of our most endangered galaxiids sharing its threat status with the more commonly known kakapo. These unique galaxiids can be found in the upper tributaries of the Clutha River upstream of Roxburgh, and two tributaries of the Pool Burn. Their remaining populations are found in less than 12 hectares of habitat.
Clutha flathead special features
Despite its oddities within populations, what does characterise Clutha flatheads, however, is a broad flattened head and thick luscious lips. They are generally golden brown with darker markings in the form of flecks and splotches all over. Some display beautiful gold and orange dustings.
Clutha flatheads are pretty cryptic and often go undetected by day, hidden amongst the gravels and vegetation. They typically grow to 100mm in length but can get up to 150mm at their largest. Don’t let their size deceive you though – these fish can be rather long-lived with adults living up to 10 years. Clutha flatheads feed on small stream invertebrates such as mayflies and stoneflies. They spawn in spring (October to November), laying tiny 2mm eggs in stream side vegetation or amongst stones.
Habitat and threats
Clutha flatheads are generally found in headwater streams and seepages small enough to step across surrounded by riparian vegetation such as grasses and tussock.
Over the last decade we have lost 35% of known flathead populations. These losses can be directly linked to a number of pressures. These include the introduction of sports fish (trout and brook char), and changes in land use such as stock access to streams, reduction of native vegetation and land development. These land use changes have been found to impact on streams and the galaxiids that live there, by increasing sedimentation, changing natural flows through water abstraction, and reducing the amount of habitat available to galaxiids to spawn.
By Lan Pham.
The unusual and rare Clutha flathead galaxias. Credits: rodmorris.co.nz