Document ID: chunk:federal_register_of_legislation:F2019L00106:body:0:p45
Version: federal_register_of_legislation:F2019L00106
Segment Type: other
Provision Reference: 
Character Range: 120021–123030

a second fishway was constructed at this road crossing, approximately 8 km upstream of Vanitys Crossing.
The construction of Googong Dam in 1978 is considered to have caused the extirpation of the Macquarie perch from the lower Queanbeyan River (i.e. from where the Googong Dam wall is now to the weir near the centre of Queanbeyan itself) (Lintermans 2002). It is likely that Burrinjuck and Wyangala Dams had similar effects on probable populations in the Murrumbidgee and Lachlan rivers downstream of these structures.
When considering fish barriers, not only 'physical' structures should be examined but also other barriers such as 'hydraulic' (e.g. areas of high velocity flow or turbulence or low flows/water levels) and 'chemical' (areas where chemical discharge causes avoidance by fish). Barriers may ocassionally have benefits for Macquarie perch in some instances by impeding the movement of pests (e.g. redfin and carp) and diseases (epizootic haematopoietic necrosis virus (EHNV)), from contacting 'quarantined' Macquarie perch populations (Lintermans 2012). Therefore, there is a clear need to balance connectivity with the exclusion of pests and diseases and their vectors (Langdon 1989a; Lintermans 2005).
Genetic diversity has been found to be higher in the Macquarie perch populations occurring in locations with a higher river slope, which correlates to a higher frequency of the species preferred 'riffle' habitat (Faulks et al., 2011). Additional correlations have been found whereby more genetically diverse individuals have been sampled at areas further downstream from a barrier, had larger flow-path lengths upstream and those which occurred in streams that are colder in winter (Pavlova et al., 2017a). However, man-made barriers, of which there are many in Murray-Darling Basin areas which Macquarie perch once inhabited, degrade habitat and impede dispersal, which has likely lowered the genetic diversity in the species (Faulks et al., 2011).
The impact of barriers may be local and immediate. For example, a new barrier may prevent a local population of Macquarie perch from diurnal movements to/from feeding and sheltering locations. Barriers may also introduce longer term impacts including preventing access to spawning beds or refuges on a seasonal basis or by altering flows and stream morphology and their ability to sustain a Macquarie perch population.

6.2.4 Altered flow and thermal regimes
In their natural state, inland rivers were characterised by variable flow patterns and reasonably consistent cyclic increases and decreases in temperature seasonally. Native species, such as the Macquarie perch, were adapted to these flow and thermal patterns. Large impoundments and water diversion/extraction has altered these natural flow and temperature patterns (Walker 1985; Kingsford 2000; Lintermans 2013c).
Flow in the coastal rivers of New South Wales where the Macquarie perch occurs, is generally more consistent however altered flow regimes as a result of large dams