Largetooth sawfish
Adults are primarily found in estuaries and marine waters to a depth of , but mostly less than . Nevertheless, the species does appear to have a greater affinity for freshwater habitats than the smalltooth sawfish ("P. pectinata"), green sawfish ("P. zijsron"), and dwarf sawfish ("P. clavata"). Largetooth sawfish from the population in Lake Nicaragua appear to spend most, if not all, of their life in freshwater, but tagging surveys indicate that at least some do move between this lake and the sea. Captive studies show that this euryhaline species can thrive long-term in both salt and freshwater, regardless of its age, and that an acclimation from salt to freshwater is faster than the opposite. In captivity they are known to be agile (even swimming backwards), have an unusual ability to "climb" with the use of the pectoral fins and they can jump far out of the water; a individual jumped to a height of . It has been suggested that this may be adaptions for traversing medium-sized waterfalls and rapids when moving upriver. They are generally found in areas with a bottom consisting of sand, mud or silt. The preferred water temperature is between , and or colder is lethal.
Largetooth sawfish
All sawfish species were added to CITES Appendix I in 2007, thereby restricting international trade. As the first marine fish, there was an attempt of having it listed under the Endangered Species Act (ESA) in 2003 by the United States National Marine Fisheries Service, but it was declined. However, it was listed as "P. perotteti" under the ESA in 2011. Following taxonomic changes, the ESA listing was updated to "P. pristis" in December 2014. Sawfish are protected in Australia and the United States where a number of conservation projects have been initiated, but the largetooth sawfish has probably already been extirpated from the latter country (last confirmed record in 1961 from Nueces, Texas). Additionally it receives a level of protection in Bangladesh, Brazil, Guinea, India, Indonesia, Malaysia, Mexico, Nicaragua, Senegal and South Africa, but illegal fishing continues, enforcement of fishing laws is often lacking and it has already disappeared from some of these countries.