Galaxias fontanus

The Swan galaxias species are endemic to Eastern Tasmania and only found in freshwater streams within the Swan River catchment.[10] It is commonly found along the headwaters of the Upper Swan River, specifically in small tributaries located upstream. Within the catchment, the Upper Swan River, Blue Tier Creek and Tater Garden Creek have resided natural populations of the Swan galaxias due to the presence of the Hardings waterfall.[8] There are currently nine translocated populations of the fish that have been located within the Swan river.[11]

In 1864, brown trout (salmo trutta) was introduced into the Swan River catchment and inhabits the downstream tributaries of the Hardings Falls.[9] The brown trout is a predator to the Swan galaxias causing the species to be restricted to headwater areas.[3] Since the introduction of the trout, the historic distribution of the Swan galaxias is unknown. The trout was introduced before the Swan galaxias was discovered and formally described.[12] However, it has been suggested by Fulton that there was a widespread of the Swan galaxias population within the entire river catchment before trout colonisation.[5]

The distribution of the Swan galaxias is listed below as described by fresh water ecologist Scott Hardie (2006).[12]

Swan galaxias exist exclusively in freshwater streams that lead to large rivers.[11] It is confined to the headwaters of small streams that are inaccessible to introduced species of fish.[13] The streams occupied by the species have a low gradient and shallow waters. They’re found in forested areas with rocky pools and instream riparian cover.[12]

Larvae and juveniles are located in schools of open water in slow moving areas of runs and riffles. Adults inhabit slow flowing tide pools with abundant instream and sidestream vegetation cover.[5]

Reproductive behaviour of the fish species tends to occur in the second year of life typically in April.[7] The fish have a spawning period is an extended period of time of 3 months within the spring season (typically August and October).[6] Spawning occurs in the adult habitat with the deposition of eggs amongst the shallow marginal lotic and lentic rocky environment.[7] The number of eggs that the Swan galaxias lay range from 150 to 550 eggs and have a diameter between 2.2 to 2.5mm.[7] Larval developments prolongs over a 5 week period.[10] Once the larvae reach approximately 35mm in length, adult colouration begins. The maximum lifespan of the Swan galaxias is approximately 3 years.[6]

In aquaculture environments, Swan galaxias’ artificially fertilised eggs hatch in temperatures between 11.5 to 18.5 degrees Celsius and have a 17-day incubation period.[7]

The primary threat to the Swan galaxias is predation from exotic and introduced species. The introduction of brown trout (salmo trutt) and redfin perch (Perca fluviatilis) has seen a decline in the Swan galaxias population, in which Sanger stated there has been “two localised extinctions in the Swan River due to the predation from these introduced species”.[5] The spread of these species has confined the natural population of the Swan galaxias to become fragmented and only present in headwaters of a small number of streams.[12]

The threat of damming creeks in which the Swan galaxias inhabits can result in barriers to the species migrations, changes in flow regimes and fluctuations in stream water levels.[12] Dams can also degrade the species spawning habitat as reduced water flow can expose the rocky bottom creek floor in which the Swan galaxias lay their eggs.[9]

The clearing of vegetation for farming practices and reductions in water quality caused by urban development present are a threat to the species.[9] Poor water quality and limited streamside vegetation has been attributed to affect the distribution pattern and abundance of the Swan galaxias within the Swan River catchment.[14]

Variations in climatic conditions such as flooding and droughts affect the population of the Swan Galaxias. Since the species inhabit small headwater streams, fluctuations in water levels are accredited to threaten the population of the species.[4] Because of the introduced exotic species occupying the downstream, the Swan Galaxias are not able to refuge from floods or droughts that affect the headwaters.[15] In 2011, floods occurred in the Swan River and resulted in the population of the Swan Galaxias to decline by 74%.[16]

The Swan galaxias is a threatened species listed as Endangered under a state, national and global level. It was classified as an Endangered species by the IUCN Red list under the Environment Protection and Biodiversity Conservation Act 1999.[11]

The fish was listed as Endangered under the Australian Federal Environment Protection and Biodiversity Conservation Act 1999 (EPBC).[14] In effect under the EPBC Act from 10th of November 2006.[11]

Tasmania has also classified the protection of the fish under the Threatened Species Protection Act 1995 (TSP).[14] The species has also been listed as a ‘priority species requiring consideration’ under the Tasmanian Regional Forest Agreement 1997.[11] Under this agreement, the species is protected through the Comprehensive, Adequate and Representative reserve system (CAR).[9]

It is listed as Endangered due to the species limited distribution and abundance, habitat destruction and as a result of predatory species. As suggested by the Australian Government, there has been a “decline in the population over the last 10 years and it is continuing decline”.[13]

Since the discovery of the fish species, the Swan galaxias’ natural distribution has become restricted and fragmented confining three populations to a limited amount of streams and to those extreme headwaters.[13]

The limited abundance of the species has been attributed by Scott Hardie as the consequence of habitat degradation.[12] Habitat degradation includes the impacts of sedimentation and reductions in water quality as a result of urban development, agriculture and forestry practices.[12] As well, the global threat of climate change results in rising water temperatures which results in a loss of water from headwater streams occupied by the Swan Galaxias.[17] As the species requires specific aquatic environments for spawning, the exploitation of water by dams heavily impacts the amount of water present in the Swan Galaxias habitat.[18]

Predation and competition from exotic species has been a reason for the species conservation listing. Since the introduction of the brown trout (salmo trutt) and redfin perch (Perca fluviatilis) there has been a decline in the Swan Galaxias species.[11] Primarily, due to the inability for both species to inhabit the same environment together due to competition and predation.[11]