(including salinity) reliance on groundwater supplies’ (Logan fact sheet), poor groundwater quality (including high salinity) may impair MI population persistence. Seasonal table fluctuations 13. As MI plants are thought to have a deep root system and may have ‘some reliance on groundwater supplies’ (Logan fact sheet), excessive or sustained groundwater drawdown may impair the species’ population persistence. ) 1 1 1 Flow regime of Purga Creek 14. Assuming overbank flows from Purga Creek are relevant to the wetland and the MI forest, altered flow regimes may change inundation patterns, impairing MI population persistence. 1 Agriculture bordering the Nature Reserve Extraction of groundwater 15. Groundwater extraction for agricultural use may the water table, reducing access by MI plant roots and impairing the species’ population persistence. 1 Extraction of surface water 16. Surface water extraction from the Bremer River and Purga Creek for agricultural use may reduce the very occasional flooding from the river into the wetland, altering the inundation regime and impairing MI population persistence. 1 Increased contamination risk from chemicals 17. Agricultural chemicals carried in runoff are likely to impair MI population persistence. 1 Increased edge effects from land clearance, tracks, fence lines, etc. for agriculture. 18. Land clearance for agriculture around the Nature Reserve causes edge effects: “MI communities are likely to be negatively impacted by edge effects such as weed invasion, increase in wind and evaporation, and changes to solar radiation and temperature changes”. ) 1 1 1 Altered rates 19. Sedimentation from agricultural 1
hydrological changes could influence the structure and composition of the swamp community. Bayesian network To demonstrate how a causal model can be framed in a Bayesian network, a model was developed in the workshop on the basis of the influence diagram (Figure 4.8), but not populated. Note that the states of the variables when populated would capture a control model versus a stressor model. A Bayesian network example (Figure 4.9) was presented to allow workshop participants to gain an understanding of how a Bayesian network is developed, populated and used for running some scenario analyses. The participants were able to follow the Bayesian network example with a temporary set of chosen probabilities as an example of how the wet and dry phases could be captured within the model. For example, increased groundwater drawdown and increased temperature would stress most components of the vegetation community, under especially dry conditions, potentially leading to the elimination of some species. This example focuses on impacts of groundwater drawdown on a Melaleuca community in wet and dry phases. Note this model is for demonstration purposes only to depict how a BN would predict an outcome. The underlying probabilities are only an example. Thus the model does not portray a realistic scenario of a system. Figure 4.9 Example of a small Bayesian network The next steps for this model would be to: carefully define a specific, measurable ecological endpoint (e.g. recruitment, adult survival) define states for all nodes determine whether data and/or expert knowledge are available to populate the model or any of its component variables. The Bayesian network can consist entirely of empirical evidence or expert opinion or can be a mixture of these or other knowledge sources (e.g. output from another model). do an initial parameterisation by populating the conditional probability tables from a range of inputs, including expert knowledge and field and simulated data. Gunnedah case study: conceptual model for silver perch Silver (Bidyanus bidyanus) was chosen as a case-study example to explore the process of developing a species-specific ecological conceptual model and its accompanying narrative table for a given species at a specific location. The chosen endpoint was the persistence of a silver perch population in the section of the Mooki River at its confluence with Quirindi Creek. A desktop survey of relevant literature (Appendix A) was used to generate the control
species by humans plants Typha may constrain waterways and restrict fish migration. references therein Compete with native water plants Although native water plants provide habitat for the prey of SP, and SP have been found in stands of Phragmites, it is likely exotic plants could play equivalent roles as habitat. Therefore, this is likely not a serious threat to SP. Cadwallader (1979) 1 1 1 Exotic fishes Carp Carp may threaten SP through competition for food resources and by increasing sedimentation through their feeding habits. DSE (2005) 1 2 2 Gambusia Gambusia are not considered a major threat to SP. NSW DPI (2006) 1 2 2 Fish diseases Exotic fishes such as carp and gambusia may be major vectors transmitting diseases to SP. Epizootic Haematopoietic Necrosis Virus (EHNV) is a particular concern in NSW (NSW DPI 2006). Langdon (1989); Glazebrook (1995); Whittington et al. (1995); Dove et al. (1997) 2 2 3 Fishing Commercial and recreational Removal of SP As commercial and recreational fishing for SP are illegal, this NSW DPI (2006) 2 2 3
Appendix A - Case conceptual model for Silver Perch Species: Silver Bidyanus bidyanus (Terapontidae) EPBC Act status: Critically endangered and on the Qld Govt WetlandInfo indicator list (Silver perch – Bidyanus bidyanus, WetlandInfo, Department of Environment and Heritage Protection, Queensland, <>). Listed as Vulnerable under the Fisheries Management Act (NSW). Conceptual model goal: Identify main factors affecting attributes of Silver Perch (SP) such as body condition and population size in a section of the Mooki River with [full conceptual model] and without [control conceptual model] water-related impacts from coal seam gas and coal mining development. Bounds: Spatial scale: Mooki River at confluence with Quirindi Ck [includes consideration of migration movements]. Temporal persistence into foreseeable future (30-y project life, 50 y). Species’ biology notes: Mainly from ), ), ) and references therein. General: This species has been well studied in culture conditions but its natural ecology is poorly (NSW DPI 2006). They appear long-lived (aging studies up to 27 y ()). In wild, are sexually mature at 3 to 5 y (based on gonad examinations (). Natural range: Includes most of the Murray-Darling drainage division, excluding the cool, higher altitude upper reaches of streams on the western side of the Great Dividing Range (). In NSW, SP now absent from most of their natural range (NSW DPI 2006) and now there are very few self-sustaining populations (DSE 2005; NSW DPI 2006). Habitats: Include rivers and large streams, as well as lakes and impoundments. Occurs in cooler, clearer, upper reaches of the Murray-Darling River system on the eastern side of the Great