A further quandary concerning rediscoveries arises
A further quandary concerning rediscoveries arises in habitats modified and frequented by humans, where rediscovered species may occur through accidental or deliberate introductions (Metcalf et al., 2007) rather than having persisted despite adverse conditions. Confusion regarding origin could evoke conflicting management priorities ranging from urgent conservation action, a ‘do nothing’ approach, to invasive species control (Crees and Turvey, 2015). As a response to presumed regional extinction, in circa 1997, M. adspersa were translocated from northern MDB tributaries to the southern MDB at a small, isolated artificial wetland, the Murray Bridge ‘Army Range Wetland’ (Pierce, 1997) (Fig. 2). A KB-R7943 mesylate was established and plans were made to release some fish to the wild, but it is unknown if these were implemented (Hammer et al., 2012, Wager and Jackson, 1993). The Army Range Wetland is only 10km from Jury Swamp, suggesting that the rediscovered fish might have been derived from the translocated population. Mogurnda species are also sold as aquarium fish in nearby Adelaide (population of 1.25 million people) and could have easily been transported to the Murray.
The possibility of translocation provided reason to question the origin of the rediscovered population. Furthermore the rediscovery occurred in an area of intense human activity (angling, boating, houses, dairy farms, drains, levees and introduced plants). As a consequence, government agencies were not persuaded to implement a formal conservation programme. Fortunately, during wetland drawdown some of the last remaining fish were rescued into captivity by a non-government organisation as the basis of a captive breeding programme, on the assumption they could be native to the area (Hammer et al., 2013).
This paper documents a research programme that ran parallel to, and informed, evolving conservation measures for southern MDB M. adspersa. Our aims were to (1) assess the population status of M. adspersa in the field, and (2) investigate genetic divergence and population heterogeneity using both nuclear and mitochondrial DNA markers in order to determine population origin (Hickley et al., 2004, Miller et al., 1989, Waters et al., 2002). In retrospect, we consider how an effective precautionary management response might be developed for application to comparable situations in the future.
Discussion Extirpation of freshwater biota is the trend for degraded river systems, and second chances for conservation are rare (Matthews and Marsh-Mathews, 2007, Miller et al., 1989, Taylor et al., 2001). Native fish populations of the MDB have undergone major declines, with M. adspersa symptomatic of this change, shifting from being a common widespread lowland species to one presumed extinct from the southern MDB for 30years (Hammer et al., 2009, Lintermans, 2007, Walker and Thoms, 1993). Our chance find of a population in a small wetland (Jury Swamp, South Australia) highlights that rediscoveries may happen anywhere, including highly altered environments, and these events should be celebrated, in the appropriate socio-political context (Scheffers et al., 2011).
Financial support was provided to MPH through an Australian Post-Graduate Award (# 1063724) and a supplementary scholarship from the CRC for Freshwater Ecology (E.822). Funding to support parts of the field study was provided by the South Australian River Murray Catchment Water Management Board (now Natural Resources, SA Murray–Darling Basin) (project 181C). Funding for conservation actions are covered elsewhere (Hammer et al., 2013). Study design, analysis and reporting, and the decision to submit this article for publication, were undertaken by the authors independently of the funding bodies.