The SMALLTOOTH SAWFISH gets its name from the Greek word PRISTIS, meaning “saw” and “small teeth that line the edges of its saw”, which are not as large as those of other members of the sawfish family.
The sawfish has a flattened shark-shaped body, brown to bluish-grey in colour, with a white underside, and wing-shaped pectoral fins. The “saw” is a quarter of the length of the body, and has between 25-32 pairs of small, sharp teeth which are longer and less broad towards the end of the “saw”. The mouth is on the underside and contains 10-12 rows of teeth in both jaws. The upper-side of the sawfish is covered in rough tooth-like scales and the under-side is coated in smooth tooth-like scales.
For many years, rarity of seeing a sawfish in the wild prevented scientists from collecting conclusive evidence about the use of their distinctive “rostrum”. This led them to falsely assume that the sawfish, like many other marine vertebrates with a “rostrum”, follow the rule that the appendage is used to either sense prey or capture prey, but never both. There are no other highly studied marine animals, with similar “rostral” characteristics, that have shown that the “rostrum” is used for both these feeding techniques. Recent studies have demonstrated, however, that the sawfish utilise their “rostrum” to both sense and manipulate prey.
A sawfish’s “saw” is made up of 1000s of “sensory organs”, that allow them to detect and monitor the movements of other organisms, by measuring the “electric fields” they emit. The “sensory organs” also called “ampullary pores” are packed most densely on the dorsal side of its “rostrum”. This allows the fish to create an image of the “three-dimensional” area above it, even in waters of low-visibility. This provides support for the “bottom-dwelling” behaviour of sawfish, utilising the “saw” as an “extended sensing device”. Sawfish are able to “view” their entire surroundings by maintaining a position low to the sea floor.
The sawfish uncovers sand-dwelling crustaceans and mollusc, two common prey types, by using their unique anatomical structure as a tool for digging and grubbing about in sand or mud. The sawfish churns up the sea bottom with their exaggerated “rostrum” to uncover these hidden food sources. Small-tooth sawfish have been observed to approach large shoals of fish while striking their “saw” rapidly from side to side. Due to the high density of small fish in a shoal, there is a high probability that the sawfish will hit, stab, stun or kill several prey during one shoal attack. The sawfish has also been observed to attack larger prey by using their weapon to dislodge large pieces of meat from victims. They then use their “serrated” saw teeth to tear through flesh. The small-tooth sawfish is predated on by sharks, but only when it is young and undersized.
Little is known about the life cycle of the sawfish, but it is thought to breed year round in areas of constant climate, but elsewhere, only in the summer Fertilisation is internal an the “pups” develop inside the female, who gives birth a year later to about 15-20 “pups”. The “saws” of the new-born are “sheathed” & “malleable” at birth for protection. The “pups” are around 60cm long at birth. The historical distribution of this species is worldwide, although recent declines in number mean that the sawfish is now absent from many sites. In American waters, the small-tooth sawfish used to be prevalent in coastal areas from New York, around the Floridian Peninsula as far as Texas. The small-tooth sawfish can exist both in salt water and freshwater, tending to prefer fairly shallow water with muddy or sandy bottoms such as rivers, streams, lakes, creeks, bays, lagoons and estuaries. Although the sawfish prefers depths of no more than 120m, it will cross deep oceans to reach new areas of coastline.
The Small-tooth sawfish is classified as Critically Endangered on the IUCN Red List and as Endangered under the United States National Marine Fisheries Service. The small-tooth sawfish has been over-fished both intentionally and as catch. Accidently caught, sawfish are rarely returned to the water alive as they are difficult to entangle from nets are dangerous to fishermen. They are caught for sport, for food and for their oil, which is used to make soap, medicine and for polishing leather, as well as for their “saws” which are removed and sold as “curios”. Habitat modification is also contributing to the decline of this species, which is slow to recover from ‘population crashes” due to “slow maturation” and ” a long reproductive cycle”.
Florida has established 3 wildlife refuges to protect the habitat of the small-tooth sawfish, in the hope that the numbers might increase sufficiently for re-colonisation of other areas. It has been protected from harvesting, in Florida, since 1992 and over the rest of American waters since 2003. Research into small-tooth sawfish life history and population distribution, as well as education and awareness initiatives may help prevent further decline of the species, but these efforts must be made worldwide to ensure the protection of this “amazing fish”.