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 7 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year N on -h at ch lin g de ns ity (s ig ht in g/ km ) The current survey and monitoring data provides a measure of the population trend at the sampling sites and by extrapolation a demonstration of the trend for the total population. These statistics do not provide a measure of the total number in the population. Understanding the population trend (declining, stable or increasing) is the primary requirement in making informed management decisions and adjusting harvest parameters. The population of Saltwater Crocodiles in the Northern Territory continues to increase as demonstrated by the trend in the pooled data from monitored rivers (Figure 1) and individual rivers (Appendix 3). In some rivers rates of increase have recently slowed and may be approaching relatively stable levels (Delaney et al. 2008; Fukuda et al in prep). There is no suggestion that trends in population differ among rivers in catchments that are unharvested, partially harvested, or subject to harvest throughout their area (Appendix 3). The continuing increase in the Saltwater Crocodile population is also demonstrated by: The biomass of crocodiles in all of these rivers continues to increase, including rivers in which increase in numbers is levelling off (Appendix 3). This is consistent with the expectation of the maturing size and age structure of a large, slow-growing species that is recovering from the threshold of extinction in the 1970s. The distribution of Saltwater Crocodiles is expanding upstream into additional accessible freshwater habitats in the Northern Territory (Letnic and Connors 2006). There is an increase in the number of crocodiles that are living in other marginal habitat, such as the coasts and seas (Nichols and Letnic 2008). The number of crocodiles removed from the no tolerance zone in the Darwin Harbour has been increasing in recent years (Table 2), indicating that animals in expanding populations continue to disperse in search of living areas (Delaney et al. 2008). Figure 1: Density of non-hatchlings (> 2 ft including eyes-only) C. porosus of all the regularly monitored rivers except for the Glyde River (source: Fukuda et al in prep). Open symbols are those from spotlight surveys and closed symbols are the counts predicted 1) from the agetotal length relationship in Webb et al. (1984) for years before 1980; and 2) as the mean of adjacent surveyed years for years after 1980. All the predicted counts except for 1973 include true survey counts in some rivers.