A sawfish once plentiful, now restricted to mostly Florida in the USA
The Smalltooth sawfish (Pristis pectinata) is a species of sawfish in the family Pristidae. It is found in shallow tropical and subtropical waters in coastal and estuarine parts of the Atlantic. We do see them locally here in Jupiter, Florida between Hobe Sound, Jupiter Island and Jupiter, Florida. Known estuaries here in Florida include the Caloosahatchee and Peace rivers.
Family: Pristidae – Sawfish
Super Order– Batoidea
Common Name– Rays
Common Name– Sawfish
Average Size and Length: The Smalltooth sawfish is thought to reach a total length of up to 25 feet, but this is likely an exaggeration. The largest confirmed size is 18.2 feet.
Average Weight: The maximum recorded weight of the Smalltooth sawfish is 770 pounds.
Teeth and Jaw: Sawfish have 10 to 12 rows of teeth in their jaws, located ventrally on the body. The upper and lower jaws have approximately 88-128 and 84-176 teeth. These teeth are small and rounded.
The rostral teeth of a sawfish are actually specialized denticles. Rostral teeth will not grow back if lost; however, teeth that are chipped will continue to grow as long as the base remains intact (Slaughter and Springer 1968).
Head: The Smalltooth sawfish has a narrow rostrum with 20–32 rostral teeth on each side. The rostral saw of the Smalltooth sawfish comprises approximately 21%-30% of the body’s total length.
Denticles: Dorsally, the denticles of Smalltooth sawfish are blunt and ovate in shape with low pedicels. This area the skin is rough. The smallest denticles are found toward the outer margins of the fins and on the head, just anterior to the eyes. Ventrally, the denticles are blunt, varying from round to oval to rounded sub-polygonal, and lack pedicels. The fact that they lack pedicels makes the ventral side smoother to the touch than the dorsal side. Denticles are so prolific ventrally that the skin is barely visible (University of Florida, 2018).
The saws of newborns are completely devoid of denticles; however, by the time the animal reaches 4.5 feet, the saw is completely covered in denticles. Denticles on the midzone of the saw are similar in size to those located ventrally, but become larger toward the saw edges (University of Florida, 2018).
Tail: The lower lobe is almost non-existent.
Demographic, Distribution, Habitat, Environment and Range: The Smalltooth sawfish is found in tropical and subtropical parts of the Atlantic, including the Caribbean and Gulf of Mexico. Its original range was the smallest of the sawfish species, covering about 810,000 square miles. In the west it once ranged from the United States to Uruguay and in the east from Senegal to Angola.
Smalltooth sawfish are mostly found in coastal marine and estuarine brackish waters. It prefers water less than 26 feet deep, but adults are occasionally seen offshore at depths of up to 400 feet. During periods with increased salinity, juveniles have been seen far up rivers. We can confirm firsthand that here in Jupiter, Jupiter Island and Hobe Sound, we see groups of between 5 and 7 Smalltooth sawfish a few times a year just offshore at depths of between 82 and 115 feet deep. In 2017, a group was discovered, and photographed within a full week in August between Jupiter Island and Hobe Sound. In 2018, most recently, one was at a depth of around 102 feet in Jupiter in the first week of December. In this known location, water temperature ranges greatly because of rapid moving thermoclines up and down the water column. The warmer temperatures may very well be at the bottom, ranging from 60s-70s F, and through the current moving thermocline, the 50s. Smalltooth sawfish are mostly found in places with soft bottoms such as mud or sand, but may also occur over hard rocky bottoms or at coral reefs. They are often found in areas with mangrove or seagrass. The lower water temperature limit is 61–64 °F. Any lower than that could be fatal to them. In the Florida Keys, they are known to be at the deeper depths, around a few shipwreck locations. Other personal known favorite estuaries are the Caloosahatchee and Peace rivers here in Florida (Dr. A Fields, 2015).
Diet: Common prey of Smalltooth sawfish are sand dwelling crustaceans and mollusks.
Large sharks are known to prey upon smaller Smalltooth sawfish.
Aesthetic Identification: The sawfish is easily recognized by its flattened body and wing-like pectoral fins. The mouth and gill slits are located ventrally and the eyes positioned dorsally. The dorsal side of the Smalltooth sawfish is brownish-grey or even bluish-grey or sometimes blackish. It is counter-shaded underneath whiteish in color. The smalltooth sawfish has a leading edge of the dorsal fin that is placed above the leading edge of the pelvic fins. It has short pectoral fins.
Biology and Reproduction: The Smalltooth sawfish is ovoviviparous. Their gestation period is not known, but research suggests long. In Florida, increased catch records of gravid females and juveniles in late spring and early autumn suggests that Smalltooth sawfish give birth between November and July, with the peak period occurring between April and May (Poulakis, 2011). The saws of the pups are fully developed and sheathed upon birth in order to prevent injury to the mother when passing through the cloaca.
Observations show that smalltooth sawfish may participate in precopulatory behavior in captivity, like courtship biting of the pectoral fins. There is sexual dimorphism in the teeth of Smalltooth sawfish. Males have a higher mean value for both left and right rostral tooth counts. The electrosensory system is believed to be used in the courtship behavior of sawfish. Reproductively active males use the sensory organs in their saw to locate females, and females will do the same to locate males.
In one very interesting recent study, Smalltooth sawfish have been observed, for the first time, to reproduce parthenogenetically in the wild; virgin birth. About 3 percent of the sawfish living in a Florida estuary (specifically the Caloosahatchee and Peace rivers) are the result of parthenogenesis. The research team speculates that since Smalltooth sawfish are so rare, females might sometimes fail to find a male during the mating season, inducing the parthenogenetic process.
Behavioral Traits, Sensing and Intelligence: Sawfish utilize their rostrum to both sense and manipulate prey. The rostrum or saw had thousands of ampullae of Lorenzini covering it. The function is to detect and monitor the movements of other organisms by measuring the electric fields that they emit. It is extremely useful in environments of low visibility. Think of it like a metal detector tool we may use. We sweep it from side to side covering an area, responding to the strongest electrical current emitted by an object forced from the created electrical magnetic field that the metal detector creates. The dorsal side of the rostrum has the most densely packed ampullae of Lorenzini. Based on this natural engineering marvel, it makes sense why sawfish remain low to the sea floor. Sawfish uncover sand dwelling prey by sweeping and digging into the sand or mud, this also churns up the bottom, uncovering the hidden prey items.
Smalltooth sawfish have been observed to approach a large shoal of fish, and even a possible school of fish while striking their saw rapidly from side to side. Due to the high density of small fish, there is a high probability that the sawfish will hit, stab, stun, or kill several preys during one group attack.
Biologist Barbara Wueringer, of the University of Queensland, demonstrated that sawfish use their rostrum to detect and manipulate prey. She observed the animals’ reaction to food already at the bottom of the tank, food falling from the water’s surface, and introduced electric dipoles. When the sawfish came across scraps of fish resting on the bottom of the tank, it used its rostrum to pin the “prey” down as it swam over and engulfed it. When food was identified as it fell through the water, the sawfish would approach its “prey” from the side and swiftly strike to impale the victim with the teeth of its saw. Both of these cases support the respective digging and attacking behaviors expected from feeding sawfish in the wild. In order to show that sawfish use their beak to sense their surroundings, Wueringer placed electric dipoles throughout the tank to simulate the electrical signals that surround moving prey. Just as the sawfish displayed different aggressive behaviors towards the “prey,” they also responded differently based on the electrical signals they received by either avoiding or approaching the signal source. With this evidence, the sawfish is now regarded as the only jawed fish to use its rostrum for both prey detection and manipulation.
**(Barbara Wueringer, of the University of Queensland, 2012: Wueringer, B.E.; L. Squire Jr. & S.P. Collin (2009). “The biology of extinct and extant sawfish (Batoidea: Sclerorhynchidae and Pristidae)” Wueringer, Barbara E.; Squire, Lyle; Kajiura, Stephen M.; Hart, Nathan S.; Collin, Shaun P. (1 March 2012). “The function of the sawfish’s saw“).**
Sawfish also use their rostrum to defend themselves.
The lifespan of the Smalltooth sawfish is unknown and unconfirmed. Some suggest between 30 and 60 years).
Smalltooth Sawfish Future and Conservation: Smalltooth sawfish are extremely vulnerable to overexploitation because of their tendency for entanglement in nets, their restricted habitat, and low rate of population growth. They are listed as critically endangered. It has been extirpated from most of its range, only surviving in about 19% of its total historical range (spanning over 47 countries). It is the only sawfish that certainly still survives in the United States (the Largetooth sawfish, has likely been extirpated from the USA). In the USA, it represents only 5% of that total historical range. Today it is essentially limited to Florida. In the Everglades region of Florida, the population is now stable and possibly slowly rising. Other countries where it certainly survives are the Bahamas, Cuba, Belize, Honduras and Sierra Leone.
Small numbers are maintained in public aquariums in North America with studbooks listing 12 individuals (5 males, 7 females) in 2014. The only kept elsewhere are at a public aquarium in Colombia. It is the only species of sawfish that has been bred in captivity.
Sawfish are highly valued for their fins used in shark fin soup and their saws sold as novelties. Their meat is used for food, and in the past, their livers were used for oils.
Sawfish have been protected in Florida waters since 1992, when a state ban on both commercial and recreational fishing was first implemented. On April 1, 2003 the U.S. National Marine Fisheries Service placed the Smalltooth sawfish on the Endangered Species List, making it the first marine fish species to receive protection under the Endangered Species Act.
The Smalltooth sawfish is protected, and International trade in sawfishes is illegal, however illegal trafficking still occurs unfortunately. The Smalltooth sawfish is also considered a prized gamefish, mainly due to its fight on the line (International Sawfish Encounter Database 2018).
Smalltooh Sawfish Recorded Attacks on Humans: Not a threat to humans. However, the Smalltooth sawfish will defend itself with its saw by thrashing it from side to side, if threatened or captured. It will cause serious injury.