Sawfish, also known as carpenter sharks, are a group of cartilaginous fish distinguished by their long, flattened snout, which resembles a saw. Among the largest fish in the world, they belong to the family Pristidae within the order Rhinopristiformes, 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 extant species of sawfish divided into 2 extant genera. They are hunted for their teeth, fins, and saws and are thus listed as Critically Endangered (CR) in the IUCN Red List.
The largetooth, smalltooth, and green sawfishes are one of the largest fishes in the world, typically measuring around 6 m (20 ft) in total length. Their largest individuals generally reach over 7 m (23 ft) and weigh as much as 500 to 600 kg (1,102 to 1,323 lb). However, according to some reports, one individual attained a length of 9.14 m (30 ft) and weighed around 2,400 kg (5,300 lb).
The narrow and dwarf sawfish are the smallest of all, reaching lengths of up to 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). These teeth are not a part of the true dentition but 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 earliest undisputed fossils of sawfish date back to the Cenozoic Era (around 60 million years ago), which follows the Cretaceous-Paleogene Extinction Event. These 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 largetooth sawfish, are present.
Although they typically inhabit marine and estuarine brackish waters, they 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 varieties 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.
They thrash their rostrum sideways, slashing large predators during a fight. Though generally harmless to humans, sawfishes react violently when captured.
On average, these fish live between 25 to 30 years in the wild, though they tend to live longer in captivity. For instance, a green sawfish individual was recorded to survive up to 35 years in captivity, while a smalltooth sawfish lived up to 42 years. In fact, all species of the genus Pristis are expected to surpass 50 years.
In contrast, the narrow sawfish, the short-lived of all extant species, has an average lifespan of about 9 years in the wild.
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 clones parthenogenetically (without fertilization by males).
The gestation period ranges from 5 months in largetooth sawfish to about a year in the smalltooth sawfish. They give birth to anywhere between 1 to 23 young, 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) to prevent 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 to 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.
Despite the lack of proper research, it is estimated that anywhere between 200 and 5000 individuals are left in the world. The constant decline in sawfish populations is largely due to habitat loss, hunting for their fins, teeth, and saws, as well as their use in traditional medicine.
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