Status of galaxiid fishes in Tasmania, Australia: conservation listings, threats and management issues

Abstract

ABSTRACT1. Fish of the family Galaxiidae are restricted to the southern hemisphere where they occupy a diverse array of habitats ranging from over 2000 m in elevation to sea level. Some species are diadromous and, hence, freshwater, estuarine and marine habitats are used during their life-cycle; other species complete their entire life-cycles in freshwater environments.2. Tasmania has a diverse galaxiid fauna that accounts for 64% of native freshwater fish species found on the island. The Tasmanian galaxiid fauna is characterized by high species richness (5 genera and 16 species), endemism (11 species), restricted distributions, and non-diadromous life histories (11 species).3. The galaxiid fauna of Tasmania has significant conservation status with 69% of species considered 'threatened'. The conservation status of the fauna is recognized at State, national and international levels.4. The key threats to galaxiids in Tasmania are exotic species, hydrological manipulations, restricted distributions, general habitat degradation and exploitation of stocks.5. Although work has recently been undertaken to conserve and manage Tasmanian galaxiid populations, the fauna is still thought to be imperilled. Knowledge gaps that need to be addressed include the biology and ecology of most species (e.g. reproductive biology, life histories, habitat use and requirements) and impacts of habitat manipulations, as well as mechanisms and impacts of interactions with exotic species. Techniques to monitor accurately the status of galaxiid species and their populations need to be developed and the coexistence of some galaxiids with introduced salmonids should also be examined.

Climate change and its implications for Australia's freshwater fish

“…Tasmania's unique freshwater environment is characterised by an extensive network of lentic water bodies, particularly in the state's Central Plateau region (Table 1; Hardie et al 2006), resulting in a highly endemic fish fauna (Allen et al 2002). This region's 10 endemic galaxiids naturally have restricted distributions; however, the additional impacts of predation by alien fish species and anthropogenic catchment and waterway manipulations for hydro-electricity generation (Hardie et al 2006;Stuart-Smith et al 2007), irrigation and recreation have resulted in distributions being further constrained.…”

“…This region's 10 endemic galaxiids naturally have restricted distributions; however, the additional impacts of predation by alien fish species and anthropogenic catchment and waterway manipulations for hydro-electricity generation (Hardie et al 2006;Stuart-Smith et al 2007), irrigation and recreation have resulted in distributions being further constrained. Limited lifehistory and physiological-tolerance information is available for most of the galaxiid endemics; however, they are thought to be adapted to predictable and relatively benign conditions, and thus to be sensitive to environmental change.…”

“…In general, climate change is likely to increase the risk of population decline for many of Tasmania's endemic galaxiids proportional to projected hydrological change. These risks, however, need to be put into perspective with existing threatening processes (Hardie et al 2006), particularly alien species, irrigation development and hydro-electricity generation.…”

A shift in the habitat use pattern of a lentic galaxiid fish: an acute behavioural response to an introduced predator

“…Galaxias auratus is a threatened galaxiid fish naturally endemic to the turbid Lakes Crescent and Sorell on the Tasmanian Central Plateau. As with other galaxiid fishes in Tasmania, this species evolved in isolation from larger predatory fishes (Hardie et al 2006b), and is vulnerable to predation by brown trout, which were introduced into Lakes Crescent and Sorell in 1868 and are now its major predator (Stuart-Smith et al 2004). Despite being found to feed during both day and nighttime (Stuart-Smith et al 2006), there is some evidence to suggest its activity and habitat use does show a diel pattern.…”

Interspecific differences in early life‐history traits in a species complex of stream‐resident galaxiids

“…Intraspecific competitive interactions are also likely to be less intense in these larger streams (Winemiller & Rose 1992), reducing the need for a larger size at hatch (Economou 1991). It is probable that similar patterns of offspring size/fecundity trade-offs exist elsewhere in other radiations of galaxiids such as species complexes identified in Australia (Hardie et al 2006;Adams et al 2014) and thought to be present in South Africa (Wishart et al 2006). It is probable that similar patterns of offspring size/fecundity trade-offs exist elsewhere in other radiations of galaxiids such as species complexes identified in Australia (Hardie et al 2006;Adams et al 2014) and thought to be present in South Africa (Wishart et al 2006).…”