Mapping suitability of habitat for the giant freshwater crayfish, Astacopsis gouldi: background document to GIS mapping layer: Scientific Report 4

The Tasmanian Forest Practices Act 1993 requires that threatened species listed in both the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 and the Tasmanian Threatened Species Protection Act 1995 are taken into account in the preparation of Forest Practices Plans (FPPs) both on Crown land and on private land. Section D3.3 of the Forest Practices Code (2000) states that threatened species will be managed in accordance with procedures agreed between the Forest Practices Authority and DPIW. The agreed procedures include the development and implementation of endorsed management prescriptions through consultation among landowners, Forest Practices Officers and relevant specialists. The current management actions applied in FPPs for the protection of the giant freshwater crayfish (Astacopsis gouldi) habitat have been developed over the last six years by specialists within the Forest Practices Authority in collaboration with the Threatened Species Section, DPIW and other species experts (Forest Practices Board 2002). They are based on current knowledge and expert opinion and are endorsed by the Tasmanian Threatened Species Scientific Advisory Committee as required under section 96(c) of the RFA. They comply with the recommendations in the draft A. gouldi Recovery Plan current in 2000. They aim to minimise the impact of forestry operations on habitat for A. gouldi. In general they state that planning of operations carried out in catchments where A. gouldi occurs should aim to ensure maintenance of stream water quality and other aspects of habitat quality such as shading, snags, food input and free movement of individuals up and down stream. The details of the recommended actions (e.g., stream buffers) vary depending on the occurrence of A. gouldi or its habitat, size of the watercourse and type of operation. Management prescriptions for forest dependent threatened species, including those for A. gouldi, are reviewed and updated regularly by specialists within the Forest Practices Board, in collaboration with the Threatened Species Unit, DPIW, as new information becomes available. Further development of effective management prescriptions for A. gouldi, however, has been hindered by a lack of information on the characteristics of habitat important for juvenile A. gouldi (as identified in the 2000 draft Recovery Plan). A research project completed in 2004 addressed this knowledge gap and defined habitat for juvenile A. gouldi (<40 mm carapace length) in mid-catchment and headwater streams (Class 2–4 streams) (Davies and Cook 2004; Davies et al. 2005). The overall aim of this current project was to take the results of Davies et al. 2005 and couple them with information on the characteristics of habitat important to adult A. gouldi (Growns 1995; Horwitz 1990, 1991, 1994; Hamr 1990: Davies and Cook 2004, Davies et al. 2005; Walsh and Nash 2002; Walsh 2003; Webb 2001) to develop a ‘habitat suitability’ map for Astacopsis gouldi. The purpose of developing this mapping resource is to trigger the application of protective provisions of the Code, especially for Class 4 streams, in order to either protect habitat quality, or to facilitate its recovery/restoration when degraded by other existing or historical landuses. It can be used to identify locations with high existing and/or potential habitat suitability, independent of current conditions that may result from existing or historical landuse. Mapping for the current status of A. gouldi instream habitat condition (i.e. under current as distinct from natural conditions) is a separate task, and will be pursued for other applications. This current project also involved preliminary validation of the mapping layer (Davies et al. unpublished data). The validation work is ongoing and may result in modifications to mapping rules if the need arises.