Management program for the saltwater crocodile in the Northern Territory of Australia 2009-2013
Fukuda, Yusuke; Delaney, Robyn; Leach, Gregory J
Northern Territory. Department of Natural Resources, Environment, The Arts and Sport
E-Publications; E-Books; PublicationNT
The draft program is open for public comment to Friday 29 May 2009. Includes Summary document.
Date:2009-04; Made available via the Publications (Legal Deposit) Act 2004 (NT).
Crocodylus porosus -- Northern Territory; Crocodiles -- Conservation -- Northern Territory; Crocodiles -- Control -- Northern Territory; Crocodiles -- Government Policy -- Northern Territory
Northern Territory Government
60 pages : illustration, maps ; 30 cm.
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
Draft Management Program for the Saltwater Crocodile in the Northern Territory 31 include counts of the 0-2 foot size class which is accepted as equating to hatchlings (less than one year old) and so provides a measure of recruitment from the last nesting season. The key rivers monitored under this program are highly productive rivers where most crocodile harvesting occurs; that have been surveyed using the spotlight technique in the past; and for which long-term datasets are available (Appendix 3). The spotlight monitoring program focuses on the following rivers: Adelaide River This major river has the largest ongoing egg collection in the harvest program. The catchment contains two important areas; Melacca Swamp where long-term monitoring data has been collected and Djukbinj National Park, which is jointly managed between the Traditional owners and the Parks and Wildlife Service. Mary River This is a river with a particularly high density of large crocodiles. Much of the surveyed section of this river is freshwater. The freshwater sections of this river provide valuable management information about the ecology and population dynamics of crocodiles in freshwater. Daly River Floodplains in the Daly River are subject to egg harvest. Arnhem land rivers Significant harvests of eggs occur in these areas, where there is an ongoing commitment by Aboriginal landholders to a variety of sustainable use projects. It includes the Liverpool, Tomkinson, Cadell, Blyth, and Glyde Rivers. These surveys will take around 16 nights work, about half which can be done out of Darwin and will not require overnight field trips. The Arnhem land rivers and the Daly River are surveyed on two separate field trips for a total of eight nights. In addition to data collected from these rivers by the Northern Territory Government, data from the East, South and West Alligator Rivers and the Wildman River, collected by Parks Australia staff provide additional data on the status of populations in Kakadu National Park. The South Alligator and West Alligators River are unique in the data set because it is not subject to any form of harvesting. All other major rivers in the Northern Territory do have some form of harvesting. The data from the South Alligator River will be analysed to interpret whether any major reduction is due to harvesting or some other independent factor (e.g. climate change). Timing and frequency of surveys A review of the crocodile-monitoring program in 1999 indicated that the spotlight technique is a reliable method for monitoring populations and is more reliable than helicopter surveys (Stirrat et al. 2001). Using the spotlight technique, a decline of 10% in the crocodile population (in a river where residual variation in the data is relatively low) can be detected with considerable confidence (power of around 80-90%) in around four to five years with annual surveys and seven to eight years with biennial surveys (Stirrat et al. 2001). In the review process a level of 10% was regarded as relevant to the management program in the Northern Territory. Declines of greater than 10% would be picked up in a shorter period. Data collected to date suggest that the impact of egg and adult harvesting has been minimal. Given these considerations a biennial survey regime has been implemented. Every year, half the rivers are surveyed so that each river is surveyed on a biennial basis. Other individual rivers may be surveyed as necessary and appropriate.