Sawfish, also known as carpenter sharks, are a group of cartilaginous fish distinguished by their long, flattened snout, which resembles a saw. They belong to the family Pristidae within Rhinopristiformes, an order which also includes guitarfish, wedgefish, and banjo rays. This order lies within the superorder Batoidea, and hence, sawfishes are a family of rays.
These fish occupy marine, brackishwater, and freshwater habitats, where they search for food using sensory cells on their rostrum. They typically feed on fish and tiny invertebrates, such as mollusks and crustaceans.
Currently, there are 5 species of sawfish divided into 2 extant genera. They are hunted for their teeth, fins, and snouts, and are thus listed as Critically Endangered (CR) in the IUCN Red List.
The largetooth, smalltooth, and green sawfishes are among the largest fishes in the world, measuring around 6 m (20 ft) in total length on average. However, their largest individuals typically reach over 7 m (23 ft) and weigh as much as 500 to 600 kg (1,102 to 1,323 lb). Moreover, some reports state that one sawfish individual attained a length of 9.14 m (30 ft), while another sawfish was found to weigh over 2,400 kg (5,300 lb).
The narrow and dwarf sawfish are the smallest of all sawfish species, reaching lengths of around 3.2 to 3.5 m (10.5 to 11.5 ft).
Although they are rays, sawfish have a shark-like appearance with flat heads and undersides. Their upper body varies in color, ranging from dull brown, gray, green, or yellow, while their underside is usually pale white.
While members of the genus Anoxypristis are usually smooth-skinned, those of Pristis have a sandpaper-like skin texture owing to numerous dermal denticles embedded in the skin.
The most prominent part of their body, the rostrum or snout, is shaped like a saw. It is edged by a row of teeth called the rostral teeth (14 to 37 on each side). Unlike bony teeth embedded in the jaws, the rostral teeth are modified dermal denticles.
The rostrum measures about one-quarter to one-third of their total body length and is simply an extension of the skull.
Their upper jaw contains approximately 88 to 128 small, blunt-edged, true teeth, while the lower jaw holds around 84 to 176 teeth. These teeth are arranged in 10 to 12 rows on both jaws.
The name of the sawfish family, Pristidae, and its type genus, Pristis, originates from the Ancient Greek word prístēs, meaning ‘saw’ or ‘sawyer.’
Although sawfish resemble sharks, they are actually rays and belong to the superorder Batoidea. They were initially classified under the order Pristiformes but have since been reassigned to Rhinopristiformes, which also includes guitarfish, wedgefish, and banjo rays.
Currently, the five extant sawfish species are classified into two genera: Anoxypristis and Pristis.
The Cretaceous-Paleogene Extinction Event, which occurred around 66 million years ago, eliminated many dominant marine predators, leading to the gradual diversification of the lineage of cartilaginous fishes. As a result, the earliest ancestors of sawfish likely emerged around this time, with their oldest undisputed fossils dating back to the Cenozoic Era (around 60 million years ago). These fossils include members of the genus Propristis as well as the then-existing species of the genus Anoxypristis.
These fish are found worldwide across tropical and subtropical waters. Initially, they occupied a vast range, from Morocco to South Africa in the East Atlantic and the United States to Uruguay in the West Atlantic. In the Pacific, they extended from Mexico to northern Peru and were abundant across the western and central Indo-Pacific. However, this range has gradually shrunk over the years.
The narrow, dwarf, and green sawfish are now limited to Indo-Pacific waters, while the smalltooth sawfish are found in the Atlantic Ocean. The largetooth sawfish has the widest range, inhabiting the Indo-Pacific, East Pacific, and Atlantic waters.
In the United States, only two species, the smalltooth sawfish and the largetooth sawfish, are found.
Although sawfish typically inhabit marine and estuarine brackish waters, a few species are also found in freshwater habitats. While smalltooth, green, and dwarf sawfish rarely venture into rivers, the largetooth sawfish, also known as the freshwater sawfish, is known to inhabit the Amazon River and Lake Nicaragua.
Sawfish inhabit a range of depths, temperatures, and substrate types:
| Habitat Feature | Details |
|---|---|
| Depth | Typically found in shallow waters (less than 10 m or 33 ft), but sometimes as low as 1 m (3.3 ft).Though they are rarely found beyond 100 m (330 ft), one sawfish was recorded at 175 m (575 ft). |
| Temperature Tolerance | Dwarf and largetooth sawfish live between 24 to 32°C (75 to 90°F), while green and smalltooth sawfish occupy waters as low as 16 to 18°C (61 to 64°F). |
| Substrate Type | Commonly found in seagrass beds and muddy or sandy bottoms, but also in rocks and coral reefs. |
They primarily consume small fish and invertebrates, like mollusks and crustaceans. In captivity, these fish are fed about 1 to 4% of their total body weight.
Sawfish use the ampullae of Lorenzini on their rostrum to detect prey by sensing underwater movements and electrical signals. They can sense prey from a distance of about 40 cm (16 in).
When they detect prey in open water, they swiftly swipe their rostrum to stun it before bringing it down to the seabed for consumption. If the prey is already on the seafloor, they slash it on the spot or even pin it down using the underside of their saw.
If the prey is small, it is swallowed whole without being cut into pieces with their teeth.
To defend themselves, these fish vigorously thrash their rostrum sideways, slashing large predators during a fight. Though generally harmless to humans in the wild, they may cause accidental injury when captured, as they instinctively thrash in self-defense.
On average, sawfish live between 25 and 30 years in the wild, though some species live longer in captivity. For instance, a green sawfish individual was recorded to survive up to 35 years in captivity, whereas reports suggest that the oldest smalltooth sawfish survived for 43 years and 7 months. In fact, all species of the genus Pristis are expected to surpass 50 years in captivity.
The narrow sawfish is the shortest-lived of all extant species, with a maximum age of 9 years in the wild. However, theoretically, this species is estimated to survive as many as 27 years in captivity.
All sawfishes are ovoviviparous, and the females give birth to live young as frequently as once a year or every second year. Though little is known about their reproductive behavior, the males are found to use their claspers to transfer sperm to the females. The sperm fertilizes the egg internally, though, in some species, like the smalltooth sawfish, the eggs develop into genetically identical offspring without the need for fertilization (parthenogenesis).
The gestation period ranges from 5 months in the largetooth sawfish to about a year in the smalltooth sawfish. They give birth to anywhere between 1 and 23 young (depending on the species), each measuring 60 to 90 cm (2 to 3 ft) at birth. At the embryonic stage, the rostral teeth are covered by a soft cap (shed shortly after birth), which prevents them from harming the mother.
In most species, juveniles remain in coastal and estuarine pupping grounds before gradually moving upriver into waters with higher salinity. However, largetooth sawfish juveniles migrate to freshwater habitats, sometimes traveling up to 400 km (250 miles) inland, where they may remain for as long as five years.
Young sawfish belonging to the genus Pristis attain sexual maturity in about 7 to 12 years, while those in Anoxypristis mature faster, between 2 and 3 years. In general, males become sexually mature earlier than their female counterparts.
Though there are only a few natural predators of sawfish, the list includes large sharks, crocodiles, and even some dolphins.
Currently, all extant species of sawfish are listed as Critically Endangered (CR) in the IUCN Red List. They are also listed under CITES.
While there is no formal census, some sources suggest that only a few hundred individuals (between 200 and 500) are left in the US waters. The constant decline in sawfish populations is primarily due to habitat loss, hunting for their fins, teeth, and saws, as well as their use in traditional medicine.
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