Document ID: chunk:federal_register_of_legislation:F2015L01763:reg:2:p4
Version: federal_register_of_legislation:F2015L01763
Segment Type: reg
Provision Reference: reg 2 (pt 4/5)
Character Range: 16695–19635

to be top order predators and their diet consists mostly of a variety of fish and crustaceans (Stevens et al., 2005). Each of the species likely has its own prey preferences, which would also vary depending on where the animals are found. The diets of these species would also change depending on age, as larger more mature animals are thought to spend more time in the marine environment.

     2.4                Breeding ecology
Little is known about the growth rates and breeding ecology of these species. It is presumed that like other large elasmobranch species they have slow growth rates, are long lived and have low reproductive capacity. These life history patterns limit their ability to recover once populations have been depleted. There are critical gaps in our understanding of fecundity (number of pups, reproductive periodicity) as well as age at maturity for females of all five species.

     2.5                Population structure in Australian waters
Recent genetic analysis on the three sawfish species has enhanced knowledge of their population structures. This information is useful in helping assess the relative importance of each population in terms of its conservation value.
It is thought that female largetooth sawfish may return to their natal river systems to give birth and that males disperse between geographic regions to breed. An alternate explanation is that there are breeding aggregations where largetooth sawfish gather, with females returning to their natal areas to pup (Phillips et al., 2011; Phillips, 2012). The evidence supports a level of paternal mixing between populations from the west and north coast regions, and the Gulf of Carpentaria region, but highly restricted maternal gene flow. The genetic results also suggest that the east coast population may be genetically distinct – at least maternally – but sample sizes from that region are limited. Faria et al. (2013) also found two distinct haplotypes in the Australian population of largetooth sawfish. The presence of female philopatry in largetooth sawfish has implications for the conservation of this species because if local populations become diminished they may not be repopulated, at least in the short to medium term, through immigration.
Green and dwarf sawfish populations are genetically structured in northern Australian waters. Distinct green sawfish populations have been identified from the west coast, the Gulf of Carpentaria and the east coast. Distinct dwarf sawfish populations are thought to occur on the west coast, the north coast and the Gulf of Carpentaria, with no migration between these locations (Phillips et al., 2011; Phillips, 2012). Unlike the largetooth sawfish, neither the green sawfish nor dwarf sawfish exhibit large-scale sex-biased dispersal in Australian waters. Although the locations and the nature of the boundaries of these population regions remain unknown, the implication is that local