Document ID: chunk:federal_register_of_legislation:F2017L01040:body:0:p14
Version: federal_register_of_legislation:F2017L01040
Segment Type: other
Provision Reference: 
Character Range: 39941–43111

The recolonisation of impacted streams appears to be very slow (e.g. Maxwell et al. 1997), indicating that dispersal is naturally slow or that the animals available for such migrations may no longer be plentiful. The species' slow growth and relatively low fecundity compounds the problems facing recruitment into impacted areas (TSS 2006).

4.2 Current threatening processes
Current, ongoing threats to the species include illegal fishing pressure (the species is easily caught), and habitat disturbance, including siltation of waterways and modifications to flow regimes, as well as the effects of drought, flooding and climate change.

4.2.1 Habitat loss/disturbance and sedimentation of waterways
Habitat loss/disturbance includes the removal or destruction of riparian vegetation, bank erosion, removal of snags, channelisation, siltation, nutrification, toxic chemical inputs, instream barriers to movement such as culverts and farm dams, and alterations to stream flow and thermal regime (TSS 2006).
Sedimentation of waterways, particularly in the headwaters of occupied river reaches, poses a threat to the survival of giant freshwater crayfish. Headwaters have been recognised as important sources of downstream sediment, nutrient, carbon and water budgets, and, as they can constitute a significant portion of a catchment (up to 70 %), appropriate management of these areas can help to control downstream impacts (Davies et al. 2016). Channel morphology, riparian structure and in-stream macro-invertebrate community composition can all display signs of modification in response to increases in sediment transported from headwater tributaries (Gregory et al. 1991; Gomi et al. 2002). Increased sediment levels arising from agricultural and forestry related land-uses have also been correlated with decreased abundances of giant freshwater crayfish (Walsh & Nash 2002). It is has also been found that increased siltation and turbidity places increased stress on the giant freshwater crayfish's ability to transpire oxygen through the gills (Eastman & Eastman 2007). Conversely, observational evidence from a survey conducted by Pracejus (2016) suggested that adult giant freshwater crayfish may display a moderate level of tolerance to increases in sedimentation if refugia, such as submerged logs or undercut banks, are present in the landscape. However, the ability of juvenile giant freshwater crayfish to withstand increasing levels of sedimentation could not be qualified from this study.

Forestry
In forestry areas, riparian and aquatic habitats are affected by activities such as road construction, logging and the establishment and subsequent harvesting of plantation timber (TSS 2006). Effects include loss of canopy cover, increased runoff, sedimentation, and changes in hydrology (TSS 2006). In situations where streamside vegetation is removed within clear-cutting forestry operations impacts can include changes to stream flows, geomorphology, nutrient dynamics, carbon budgets and impacts to in-stream habitat (Thompson et al. 2009). These threats were known to occur in Tasmanian catchments (Jackson & Blühdorn 1999). Impacts on stream condition