378 Monitoring Threatened Species and Ecological Communities
community is listed as a threatened ecological community under the EPBC Act.
Edgbaston contains about 100 springs, ranging in size from a few square metres to
~0.5 ha (Fig. 30.1), although spring extent and morphology varies seasonally,
depending on aquifer discharge. The springs are naturally shallow (most <5 cm
deep) but some have been artificially excavated up to 30 cm deep.
When discovered in the early 1990s, red-finned blue-eye occurred in eight
discrete springs on Edgbaston. The non-government conservation organisation,
Bush Heritage Australia, purchased Edgbaston in 2008 and has since managed it
as a registered conservation reserve. A comprehensive audit conducted in 2009
revealed that the number of springs occupied by red-finned blue-eye had
dwindled to four. The species was clearly heading towards extinction
without intervention.
Threats to red-finned blue-eye
The primary threat to red-finned blue-eye is the invasive introduced fish
Gambusia holbrooki (hereafter gambusia). Although the exact mechanism by
which gambusia eradicate red-finned blue-eye is unknown, empirical evidence
demonstrates that the two species are unable to co-exist in the same spring
(Fairfax et al. 2007; Kerezsy and Fensham 2013). Gambusia inevitably becomes
the dominant – and eventually the only – fish species present in any spring it
colonises. Gambusia give birth to live young and are competitively dominant
with other species. Gambusia colonise springs during rain events that cause
overland f low, with fish able to swim between springs in a few centimetres
of water.
Reduced water discharge into the springs from the Great Artesian Basin caused
by drawdown of the aquifer threatens the red-finned blue-eye and the entire spring
ecosystem. The depth of the springs accentuates this risk – any f low reduction
could render a particular spring uninhabitable for many aquatic species.
Historically, aquifer drawdown was caused by bores sunk for pastoral purposes but
this has been ameliorated by capping and piping f lowing bores where practical.
Mining now presents the major threat to the integrity of the aquifer. Proposed coal
mining in the Galilee Basin north-east of Edgbaston may affect the rate of
discharge into the springs at Edgbaston, and groundwater extraction for mining
should therefore be considered a threat.
Pigs damage springs and spring vegetation when feeding through disturbance
and fouling. Large populations of kangaroos may also compromise water quality,
but their impact is most keenly felt through damaging infrastructure (i.e.
barrier fences).
Management interventions
Bush Heritage tackled several threats immediately upon acquisition in 2008 by
de-stocking and initiating feral pig control. These actions have been successful,