Acknowledgements V Summary VI 1 General introduction 1 1 Barred Galaxias 1




НазваниеAcknowledgements V Summary VI 1 General introduction 1 1 Barred Galaxias 1
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1.1 Barred Galaxias


Barred Galaxias (Galaxias fuscus) (Figure 1) is a small freshwater fish belonging to the family Galaxiidae. It is endemic to upper headwaters (above 400 m altitude) of the Goulburn River catchment in central Victoria. It is non-migratory and inhabits cool, clear, flowing streams with cobble or sandy substrate and their diet consists mainly of aquatic and terrestrial invertebrates (Raadik et al. 1996; 2010). Barred Galaxias are scaleless and have a yellow-orange body colour with up to 10 black, vertical stripes along the sides. They are relatively long-lived, have low fecundity and are slow growers (Raadik et al. 2010).

Barred Galaxias is listed nationally as Endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 and is also listed under the Victorian Flora and Fauna Guarantee Act 1988. The species has suffered extensive decline in range and abundance. Several Barred Galaxias populations are extinct and only twelve small, isolated populations are known to remain.

Raadik et al. (2010) identified several key threats to Barred Galaxias:

• Predation by and competition from the introduced predatory salmonid species Rainbow Trout (Oncorhynchus mykiss) and Brown Trout (Salmo trutta), hereon referred to as ‘trout’

• Surface water loss during drought

• Siltation/sedimentation

• Bushfire impacts

• Water regime changes

• Genetic isolation

The National Recovery Plan for Barred Galaxias (Raadik et al. 2010) details the species’ distribution, ecology, threats, recovery objectives and the actions necessary to ensure their long-term survival.

1.1.1 Fire impacts on Barred Galaxias


Barred Galaxias habitat from Lake Mountain to Mt Disappointment was burnt during the 2009 Black Saturday fires. This area represents 45% of the known range of the species. Barred Galaxias from several populations occurring within the 2009 fire boundary were rescued soon after the fires and maintained temporarily in captive facilities at Department of Sustainability and Environment (DSE) Arthur Rylah Institute (ARI) until habitat conditions improved, following which they were returned to their natal streams. This included Barred Galaxias from S Creek, Luke Creek, Robertson Gully, Keppel Hut Creek, Rubicon River, Little Rubicon River, Upper Taggerty River and Torbreck River South Branch (Raadik et al. 2009). Some Barred Galaxias populations were affected by fires in 2006/07 and all populations have experienced a decade of low flows due to drought conditions.

Fire poses direct and immediate or indirect and sustained impacts on aquatic ecosystems (Gresswell 1999). Its complex and diverse effects, however, depend on the extent and severity of the fire, post-fire weather conditions (e.g. rainfall intensity and duration), and the physical, chemical and biological characteristics of the catchment (e.g. geomorphology, geology) (Gresswell 1999).

During a fire event there is immediate loss of vegetation including that covering and shading streams. Fire burning adjacent to or crossing streams can increase water temperature. During the 2009 Black Saturday fires water temperatures in streams and ponds reached 55 °C (DSE 2009). Also the water chemistry and quality of streams can be altered by inputs of smoke, ash and fire retardants (Gresswell 1999; Dunham et al. 2003; Gimenez et al. 2004). The direct impacts of fire can result in immediate death or displacement of small numbers of fish to entire fish populations (Rieman and Clayton 1997; Lyon and O’Connor 2008).

Following fire events, changes in the surrounding landscape indirectly influence aquatic systems. Increases in water temperature occur primarily because of lack of riparian shading, but also due to channel simplification, topographic shading, and hydrologic changes (Gresswell 1999; Dunham et al. 2007). Loss of vegetation and changes in soil structure increase the likelihood of soil erosion, as well as greater and more variable stream flows (Gresswell 1999; Rieman and Clayton 1997). Rainfall events flush sediment and ash into streams, smothering instream habitat and causing fluxes in nutrient levels and reductions in water quality (Gresswell 1999; Lyon and O’Connor 2008; Raadik et al. 2009). Additionally, anthropogenic activities, such as post-fire salvage logging and road construction, can exacerbate post-fire impacts on aquatic systems (Rieman and Clayton 1997). Indirect effects of fire can cause local extirpation, displacement or reductions in the abundance and distribution of fish (Rinne and Neary 1996; Gresswell 1999; Lyon and O’Connor 2008). Adverse indirect impacts on fish include reduced water quality, loss of available habitat and food resources, and dramatic changes in flow conditions (Gresswell 1999). The time taken for fish populations to recover is variable and largely influenced by their life history and dispersal ability as well as habitat connectivity (Gresswell 1999; Lyon and O’Connor 2008). Fish can recolonise impacted reaches by migrating from local refugia or upstream or downstream sources (Rieman and Clayton 1997; Dunham et al. 2003). Small, isolated fish populations, particularly sedentary species, are more vulnerable to disturbance and have limited recolonisation potential because of reduced habitat connectivity (Gresswell 1999).

Barred Galaxias populations are small, fragmented and isolated; therefore they are highly susceptible to the effects of fire. Management actions are necessary to ensure the survival and recovery of threatened Barred Galaxias populations within fire-impacted areas.
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