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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2.4 Discussion and recommendations


Careful site selection is a pivotal step in planning translocation events (Minckley 1995). Translocation sites should satisfy the species’ habitat requirements to facilitate their survival, establishment and range expansion (Minckley 1995; George et al. 2009), however, not all areas within the species former range will contain suitable habitat. Differences in stream and catchment condition could make some sites more preferable than others. Preferably all known threats to the species (e.g. predation, dewatering, hybridisation, etc.) should be absent or mitigated at the translocation site. For example, instream sedimentation, commonly occurring in catchments impacted by bushfire and forestry activities, reduces water quality and degrades instream habitat, which inturn influences the survival and recovery of fish (Lyon and O’Connor 2008). Thus, sites impacted by sedimentation would be less suitable for Barred Galaxias translocation than those unaffected. Furthermore, the total stream area above an instream barrier should be large enough to support long-term population growth and range expansion of the translocated fish population, as well as being large enough to maintain the natural diversity and condition of the stream itself (Moyle and Sato 1991).

This project highlighted the scarcity of available potential translocation sites within a portion of the natural range of Barred Galaxias, due mainly to the widespread distribution of trout, extending upstream into small headwater streams. This is likely to reflect the situation in other areas within the range of Barred Galaxias in the Goulburn River system, as trout are prevalent and widespread throughout all of the cooler, upland reaches of the system. Many of these streams are likely to have historically harboured Barred Galaxias populations, which are unable to co-occur with trout (Raadik et al. 2010, Raadik T.A. unpublished data). Trout predate on, and out-compete, the galaxiids for food and habitat (McDowall 2006, Raadik et al. 2010), and as such, the remaining Barred Galaxias populations are restricted to headwater streams were trout do not occur (Raadik et al. 2010), usually upstream of instream barriers.

Identifying potential Barred Galaxias translocation sites in predator-free catchments was also difficult as very few existing natural physical instream barriers were known within the study area that did not already have Barred Galaxias upstream of them. As the conservation of distinctive native fish taxa is a prime objective in conservation translocation of threatened species (Minckley 1995) selection of potential translocation sites also excluded stream reaches known to contain populations of Mountain Galaxias as the two galaxiid species are known to naturally hybridise (Raadik 2011). Consequently, of the 217 potential sites identified for assessment the majority were in headwater reaches and small in catchment area. Only 61 of these were able to be assessed for suitability during this study as many were remote and difficult to access. The remaining potential sites are therefore available to be ground-truthed in the future if required.

Of the 61 sites visited, only four separate catchments, each without resident fish and with an effective barrier downstream, were considered appropriate for the immediate translocation of Barred Galaxias. We selected two of these that were in catchments of medium size for the forthcoming trial translocation of Barred Galaxias (see Chapter 3), to ensure that the monitoring of the trial translocation would be manageable relative to the small number of fish to be translocated. A suitable translocation site in a larger catchment (Koala Creek) was set aside for future use when translocating a larger population.

As expected, given their wide distribution, a high proportion of potential sites assessed contained trout, further extending their known range in headwater reaches. Without future management intervention, including installation of a barrier and upstream removal of trout, these sites are currently unsuitable for Barred Galaxias translocation. Many other potential translocation sites appeared to lack fish but the presence of an effective barrier downstream could not be determined. Further surveys for barriers downstream of these sites is necessary, and if none are found, the installation of a barrier is required to improve the security of the upstream reach from trout invasion before these sites can be considered suitable for translocation. That only a small number of suitable catchments were found is indicative of the difficulty of locating suitable translocation sites and the lack of remaining catchments that do not first require potentially expensive management works (i.e. removal of resident fish, installation of instream barrier) to make them suitable.

The cost of undertaking surveys for effective barriers to locate catchments suitably protected from upstream predator invasion is considered to be less than that of barrier installation in steep and remote catchments, particularly if the complete removal of any upstream resident trout is also required. Therefore undertaking barrier surveys to identify suitable translocation sites for Barred Galaxias appears more acceptable than the more costly and difficult second option. However, this is predicated on the assumption that suitably large upland catchments are not limited across the target landscape. This assumption is incorrect given the wide distribution of trout in headwater reaches and therefore barrier construction and fish removal may need to be considered in the future as a conservation management option if additional and larger sites are needed for Barred Galaxias translocations.

The success of upstream colonisation of trout is influenced by physical parameters (barrier type and height), hydrological conditions (flow and pool depth), and their jumping and darting abilities. Meixler et al. (2009) calculated the maximum jumping height and darting speed of Brown Trout (average length = 52 cm) to be 1.10 m and 4.64 m/s respectively, whilst Rainbow Trout were similar (average length 50 cm, maximum jumping height = 1.03 m, maximum darting speed 4.50 m/s). Therefore, we subjectively rated barriers as 100% effective if they were greater than 2 m in height, with no plunge pool downstream. Also the barrier needed to be effective in all flow conditions, particularly high flows. The location of a barrier in a v-shape landscape would direct water to the centre of the stream channel, even during periods of high flow, and prevent lateral water movement through which trout may migrate. Ideally, a barrier would also consist of solid rock for permanency.

The seven barriers identified in this study were greater than 2 m in height and were natural rock waterfalls, except on the upper Taponga River, where the barrier was a fall in height from the downstream side of a road culvert. There is a risk of this culvert being washed out in high flow, thus allowing the trout residing downstream to easily migrate upstream into the translocation zone. Installation of a second barrier upstream of the road culvert would further secure this site from trout invasion.

During site assessments, no sites were found that suffered from sedimentation impacts. However, three sites surveyed were dry and were therefore considered unsuitable for Barred Galaxias translocation because water security is a threat. Furthermore, upstream catchments of sites varied in size, with many relatively small in area (< 4 km 2). The degree of water permanency in a small headwater catchment, to sustain a population of Barred Galaxias, is difficult to determine and may vary over time. It could be measured by annual site visits during the low flow period or be subjectively assessed by checking for the presence of in-stream bryophytes (an indicator of water permanency).

Stoessel et al. (2012) found that Barred Galaxias lay clusters of eggs on the underside of cobbles positioned in flowing water. The presence and abundance of instream cobbles, and possibly smaller boulders, is therefore needed to facilitate breeding of Barred Galaxias. Observing and/or mapping the presence and abundance of potential spawning substrates should therefore be incorporated into the site assessment process to identify future translocation sites. The deliberate release of trout into areas upstream of barriers is also an issue, particularly at sites easily accessed by road, such as Koala Creek and Taponga River. Site inaccessibility is therefore important to decrease the likelihood of human-assisted dispersal of trout. This can be assessed by the location of the proposed site to existing roads and trails within a catchment.

To further improve the suitability of potential translocation sites for Barred Galaxias, future site assessments should therefore also incorporate evaluation of the presence of suitable spawning habitat throughout the site, degree of site accessibility, and a more detailed assessment of water permanency. Community engagement and education activities will also be important to help mitigate human-assisted trout dispersal.

Another important outcome of this project is the development of a list of secondary sites, not immediately suitable for Barred Galaxias translocation, which have been preliminarily assessed and require varying levels of works to improve their suitability. As the location and issues with these sites is already known, their suitability may be improved in the future in a relatively short time and with more strategic investment if the need arises. This is particularly pertinent if a stochastic event occurs requiring urgent translocation of a Barred Galaxias population. However, all potential translocation sites should be reassessed before a translocation event occurs in case habitat conditions have changed since the initial assessment, for example, trout may have since colonised the stream rendering the site unsuitable.

Given the scarcity of available potential translocation sites within the natural range of Barred Galaxias, due mainly to the widespread distribution of predatory trout, there is a need to create and manage trout-free zones in headwater catchments for future translocation events to ensure the long-term survival and recovery of this species. This would readdress to some extent the current imbalance in the total area occupied by indigenous native fish species in headwater reaches compared to that of trout. This issue is also pertinent for Mountain Galaxias, a species also impacted by trout (Lintermans 2000, Jackson et al. 2004, McDowall 2006, Raadik 2011), which were found to be restricted to a few, small and isolated populations in the study area. This current distribution is considered to be a fragmentation of a former widespread range.


The following actions are required to improve the success of the trial translocations and to improve the success of future Barred Galaxias translocations:

• Install a second barrier at Taponga River upstream of the 15 Mile road crossing to secure the translocated Barred Galaxias population;

• Perform barrier surveys on the 24 identified fishless sites to potentially add to the list of sites suitable for immediate translocation;

• Install barriers and remove trout from the 19 identified small headwater catchments to render them suitable for immediate translocation;

• Undertake a more rigorous assessment of site accessibility, water permanency and include assessment of the presence of suitable spawning habitat (see Stoessel et al. 2012) throughout each site in future assessment of translocation site suitability; and,

• Undertake stakeholder engagement and education regarding Barred Galaxias conservation and the impacts from human assisted dispersal of trout.


3 Trial translocations of post-fire impacted
Barred Galaxias
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