Galaxias, commonly known as galaxids, are small, delicate freshwater fish endemic to Australia. Renowned for their slender bodies and adaptability to various aquatic environments, these species play a crucial role in maintaining the ecological balance of their habitats. Among the galaxids, the Common Galaxias (Galaxias maculatus) and the Yalmy Galaxias (Galaxias sp. nov. ‘Yalmy’) are particularly noteworthy.

In addition to the Common Galaxias and the Yalmy Galaxias, Australia is home to other galaxid species such as the Shaw Galaxias (Galaxias gunaikurnai). Endemic to the headwaters of Shaw Creek in Victoria’s Gippsland region, the Shaw Galaxias is a small, stout-bodied fish characterised by a grey-brown to grey-tan colouration with darker blotches and bands. It inhabits cool, clear alpine streams and is considered critically endangered due to its limited distribution and threats from introduced species like brown trout.

Common Galaxias (Galaxias maculatus)

The Common Galaxias is a widespread species found in coastal rivers, lakes, and streams across Australia, from Adelaide in South Australia through Victoria, Tasmania, New South Wales, and southern Queensland, extending to areas of southern Western Australia. This species is also present in New Zealand, Lord Howe Island, the Chatham Islands, and parts of South America, including Chile and Argentina. It is considered one of the most widely distributed freshwater fish species globally.

Physical Characteristics

Typically measuring around 100mm in length, the Common Galaxias can grow up to 190mm. They exhibit a translucent body with a silvery sheen, often displaying a series of dark spots along their sides. Their streamlined shape and small size make them well-suited for navigating the varied habitats they occupy.

Habitat and Behaviour

Common Galaxias are highly adaptable, inhabiting a range of environments from still waters to slow-moving streams. They are capable of withstanding salinities well above that of seawater, allowing them to thrive in estuarine and brackish conditions. Their diet primarily consists of small aquatic insects, crustaceans, molluscs, and terrestrial insects, especially chironomid larvae.

Reproduction

Spawning occurs among terrestrial vegetation around river estuaries during high tides. The eggs remain submerged for two weeks or more until subsequent spring tides. Upon re-inundation, the eggs hatch, and the larvae, approximately 7mm in length, migrate to the sea. They spend the winter there and return to freshwater after about 5 to 6 months. The returning young fish are around 45-50mm long, transparent, and enter the rivers in large shoals on the rising tide. They usually reach maturity and spawn the following autumn at one year of age.

Conservation Status

The Common Galaxias is currently classified as widespread and common, with no immediate threats to its population. However, maintaining the health of their habitats is essential for their continued prosperity.

Yalmy Galaxias (Galaxias sp. nov. ‘Yalmy’)

The Yalmy Galaxias is a lesser-known species endemic to the Yalmy River in Victoria, Australia. This species has been identified as a distinct taxon, though it has not yet been formally described. The Yalmy Galaxias is considered critically endangered, primarily due to habitat degradation and the introduction of invasive species.

Physical Characteristics

Specific physical characteristics of the Yalmy Galaxias are not well-documented due to its limited distribution and the need for further research.

Habitat and Threats

The Yalmy Galaxias inhabits the Yalmy River, a small, clear-flowing stream in Victoria. The introduction of trout into the river has posed significant threats to this species, as trout are known to prey on galaxids and compete for resources. Additionally, habitat degradation from human activities, such as land clearing and water extraction, has further compromised the survival of the Yalmy Galaxias.

Conservation Efforts

Conservation initiatives are underway to protect the Yalmy Galaxias, including habitat restoration and the management of invasive species. Ongoing research is essential to better understand the species’ ecology and to develop effective conservation strategies.

Shaw Galaxias (Galaxias gunaikurnai)

In addition to the Common Galaxias and the Yalmy Galaxias, Australia is home to other galaxid species such as the Shaw Galaxias (Galaxias gunaikurnai). Endemic to the headwaters of Shaw Creek in Victoria’s Gippsland region, the Shaw Galaxias is a small, stout-bodied fish characterised by a grey-brown to grey-tan colouration with darker blotches and bands. It inhabits cool, clear alpine streams and is considered critically endangered due to its limited distribution and threats from introduced species like brown trout.

The galaxids, particularly the Common Galaxias and the Yalmy Galaxias, are integral components of Australia’s freshwater ecosystems. While the Common Galaxias remains widespread and abundant, the Yalmy and Shaw Galaxias face significant challenges that threaten its survival. Conservation efforts are crucial to ensure the persistence of these species and the health of the aquatic environments they inhabit.