Figure 3. Global distribution of largetooth sawfish (yellow) and areas of possible extinction (red). (IUCN 2013a)

The Australian populations of largetooth sawfish are likely to comprise a high proportion of the Indo-west Pacific population, and form a globally important population centre (Phillips, 2012; Kyne et al., 2013). Further, there is most likely negligible maternal gene flow in largetooth sawfish between south-east Asia and Australia. If there is genetic exchange between south-east Asia and Australia, it is likely the result of male gene flow (Phillips et al., 2011; Faria et al., 2013).

The majority of records are of juvenile and sub-adult animals (<300 cm) from rivers. They have been recorded in numerous drainage systems in northern Australia in fresh and saline water including the Fitzroy, Durack, Robinson and Ord Rivers (Western Australia), the Adelaide, Victoria, Daly, East and South Alligator, Goomadeer, Roper, McArthur, Wearyan and Robinson Rivers (Northern Territory), and the Gilbert, Mitchell, Normanby, Wenlock, Mission, Embley and Leichhardt Rivers (Queensland).

In Western Australia, largetooth sawfish have been recorded from the Fitzroy, Durack, Robinson, May and Ord Rivers. There are coastal records from Cape Keraudren to King Sound (Thorburn et al., 2007a). One large individual was also captured in south-west Western Australia, off Cape Naturaliste, however this occurrence is considered an anomaly and outside the normal range for the species (Chidlow, 2007).

In the Northern Territory, largetooth sawfish have been recorded from the Adelaide, Victoria, Daly, East Alligator, South Alligator, Goomadeer, Roper, McArthur, Wearyan and Robinson Rivers. Records for the species occurrence offshore are limited, and the data on these captures are poor. A single record is known from offshore localities in the western Gulf of Carpentaria, in the vicinity of Groote Eylandt (Field et al., 2008).

Records of largetooth sawfish from the east coast of Queensland in the last seven years suggest that they are largely restricted to the rivers draining into Princess Charlotte Bay and their distribution and abundance is patchy and low (Pillans, 2012).

It is unclear whether there are discontinuities in the coastal distribution of largetooth sawfish within their range. It is also unclear whether the lack of records from certain river systems within their area of occupancy reflects a real absence or merely limited sampling effort.