Key Threatening Process Nomination Form
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- Y e ar 1999 2000 2001 2002
Loggerhead turtle (Caretta caretta) Australian conservation status: National: Listed as Endangered, Marine and Migratory species under the Environment Protection and Biodiversity Conservation Act, 1999. New South Wales: Listed as Endangered under the Threatened Species Conservation Act, 1995. Northern Territory: Listed as Endangered under the Territory Parks and Wildlife Conservation Act, 2001. Queensland: Listed as Endangered under the Nature Conservation Act, 1992.
- Listed on Appendix I & II of the Convention of International Trade in Endangered Species of Fauna and Flora (CITES). - Listed as Endangered on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species. - Listed on Appendix I of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It has been acknowledged at many levels of government that the loggerhead turtle, Caretta caretta, is under significant threat. The species is recognised under the EPBC Act as an Endangered species, acknowledging the fact that if the species’ survival remains threatened, it may become extinct, and the recovery of the population of loggerhead turtles in Queensland is threatened most significantly by boat strike (see Table 6). Loggerhead mortality as a result of boat strike appears to be increasing, which means that boat strike has the capacity to endanger the recovery of this reduced population (XXXX pers. comm.). The loggerhead turtle is a relatively long-lived animal, with a life expectancy of at least 50 years and sexual maturity reached at between 8 and 15 years, with non-annual, periodic egg-production (NSW Scientific Committee, 2001). During the last two decades, loggerhead populations have been decreasing faster than any other marine turtle species, and it has lost up to 80% of its nesting population on the east coast (Parish, 2001). Population models were developed using long-term mark-recapture data from loggerhead turtles feeding in the Heron Island region. These models indicate that small declines in annual survival rates of adult and sub-adult loggerheads can have an extreme impact on population dynamics. It is predicted that a loss of a few hundred loggerhead turtles can lead to the extinction of the eastern Australia population within a century (Heppell et al., 1996). Anthropogenic effects and disturbances on loggerhead population growth are difficult to measure due to the large time frame taken for maturity in this and other turtle species. There is therefore a lag time between the cause and effect of declining population numbers. For this reason, immediate and drastic action must be taken to significantly reduce mortality by means of anthropogenic causes, in particular boat striking. This also demonstrates that the precautionary approach must be used here. Work et al. (2010) investigated the effects of vessel speed, vertical depth and type of propulsion system on loggerhead turtles through an experimental approach. Full-scale models with fibreglass carapaces were used in testing, with results supporting the existing view that vessel speed influences likelihood of catastrophic damage. Depth in water column was not a significant factor, while propeller guards were ineffective at planning speeds in 3-6m vessels and only slightly helpful at idle speed. Two different jet propulsion systems in a 5.8m skiff were tested: an 80hp four-stroke jet outboard and a 130hp personal water-craft with an inboard jet propulsion system. These yielded dramatic improvements in animal safety. The Department of Environment and Resource Management of the Queensland Government compiles ongoing stranding and mortality databases for marine wildlife. From 1998 until 2004, boat strike was the principal anthropogenic cause of stranding and mortality of loggerheads in Queensland (Table 6), with the Annual Reports indicating that the annual mortality rates due to boat strikes (total of 39 between 1999-2004) out-number mortality rates from all natural causes combined (5) significantly. Of the total confirmed loggerhead turtle mortalities where the cause of death could be determined contained within the Marine Wildlife Stranding and Mortality Database Annual Reports, approximately 35.8% (39/109) featured fractures and injuries consistent with boat strike and propeller damage (Table 6). Comparatively, only 22.9% of cause of death confirmed stranding and mortalities were due to natural causes such as disease and depredation, a figure which, as was the case with the green turtle, indicates the severe stress boat strike incidents are placing on non-impacted green turtle population dynamics. Table 6: Records of reported loggerhead turtle mortalities in Queensland waters from 1998-2002 showing the percentage of confirmed mortalities attributed to boat strike
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