Status and Conservation of Freshwater Sawfish in Northern Western Australia

The global population of the critically endangered freshwater sawfish (Pristis microdon) has declined as a result of habitat degradation and fishing pressure (e.g. commercial bycatch).  In areas like northern Australia, implementation and enforcement of conservation strategies for this species are difficult, due to a lack of knowledge regarding this species and the remoteness of its habitat.  Between 2002 and 2009, P. microdon were surveyed biannually, and between 2007 and 2009 were monitored via acoustic telemetry in the Fitzroy River, Western Australia.  Long-term catch-per-unit-effort (CPUE) data demonstrated significant decreases between the early dry season (June-July) and late dry season (October-November) for 0+ P. microdon, and to a lesser degree for >0+ P. microdon.  Ontogenetic differences in dispersal abilities, observed from acoustic monitoring data, and differences in natural mortality estimates of 0+ and >0+ P. microdon, is believed to have resulted in the lesser decrease in seasonal CPUE of >0+ P. microdon.  CPUE also varied between early dry seasons, with evidence suggesting variances were related to the length and magnitude of increased river stage height during wet seasons.  No short-term population decline was apparent during the study period.  Results from this study demonstrated the importance of river depth for P. microdon, and the need to prevent decreases from anthropogenic factors such as water abstraction.  Long term monitoring was valuable in that it allowed inter-annual trends in recruitment to be related to environmental conditions, and suggests that the Fitzroy River population is currently stable.  As one of the last remaining populations known on Earth, increased conservation efforts are vital for the survival of P. microdon.  This species has recently become fully protected throughout northern Australia.  Public awareness has also been enhanced through conservation efforts by researchers, including public education and community partnered programs.  These efforts have resulted in a substantial decrease in observed killings by fishers.  Practiced conservation efforts and suggested future endeavours for the protection of the species are discussed.