Sawfish
Sawfish are primarily found in coastal marine and estuarine brackish waters, but they are euryhaline (can adapt to various salinities) and also found in freshwater. The largetooth sawfish, alternatively called the freshwater sawfish, has the greatest affinity for freshwater. For example, it has been reported as far as up the Amazon River and in Lake Nicaragua, and its young spend the first years of their life in freshwater. In contrast, the smalltooth, green and dwarf sawfish typically avoid pure freshwater, but may occasionally move far up rivers, especially during periods when there is an increased salinity. There are reports of narrow sawfish seen far upriver, but these need confirmation and may involve misidentifications of other species of sawfish.
Smalltooth sawfish
Unlike the largetooth sawfish ("P. pristis"), the only other sawfish in the Atlantic, the smalltooth sawfish has a leading edge of the dorsal fin that is placed roughly above the leading edge of the pelvic fins (when the sawfish is seen from above or the side), relatively short pectoral fins and lack of a distinct lower lobe to the tail (lower lobe very small or absent). It can be separated from the more similar dwarf sawfish ("P. clavata") and green sawfish ("P. zijsron") by the distribution (both are only found in the Indo-Pacific) and the dorsal fin (its leading edge is placed slightly or clearly behind the leading edge of the pelvic fins in the dwarf and green sawfish). The smalltooth sawfish has a relatively narrow rostrum ("saw") with 20–32 teeth on each side.