Lowland longjaw galaxias Galaxias cobitinis
The lowland longjaw galaxias (or affectionately known as ‘jaws’) is one of Otago’s remarkable galaxiid species. With only a few remaining populations in the Kauru and Kakanui Rivers in North Otago and a smattering of populations in spring habitats in the Mackenzie Basin (Waitaki), the lowland longjaw galaxias is one of New Zealand’s rarest fish species. Classified as ‘Nationally Critical’ and jaws are known as the ‘kakapo’ of the freshwater world. Their remaining populations are found in less than 15 hectares of habitat.
Lowland longjaw galaxias special features
As their name suggests – these quirky, pencil-thin fish have a long bottom jaw which protrudes out over their top lip. They are among the smaller of the galaxiids, growing up to 80 mm at their largest. Their colourings are a pale lemon colour with handsome silver flecks which line their back over dark brown splotchy patterns. Their outer eyes are sparkly gold in colour. Jaws feed on small stream invertebrates such as mayfly and Chironomid larvae. They spawn in winter months (July - September) laying tiny 2mm eggs in spring upwellings.
Habitat and threats
Lowland longjaws thrive in cool springs and streams with their largest populations found amongst the cobbles and gravels in the fast flowing riffles of braided rivers. The adults need clean ‘roomy’ movable substrates so they can burrow into the cracks and crevices between rocks. In winter their young can be spotted in schools swimming in slower moving water such as pools and backwaters.
Their main threats are habitat loss from land development, the invasion of aquatic weeds which clog waterways and predation by introduced fish species. A combination of these threats has recently caused the extinction of two lowland longjaw populations.
Land-use change in the form of stock access to streams, reduction of native vegetation, land development and forest harvesting have been found to impact on streams and the species within them by increasing sedimentation, changing natural flows through water abstraction and reducing the amount of habitat available to galaxiids to spawn.
By Lan Pham.
Lowland longjaw galaxias have a distinctive ‘fat-lipped’ lower jaw: Credits: DOC freshwater team