Sawsharks are a group of sharks, popular among other sharks because of their toothy, flattened snout that resembles a saw blade. They are about ten species, within two genera. These sharks inhabit the deep continental shelf of temperate, subtropical, and tropical oceans.
Despite being in a completely different family, Saw sharks are often confused with Sawfishes because of their almost identical similarities. However, there are several distinguishing features between the Sawshark and the sawfish.
Kingdom – Animalia
Phylum – Chordata
Class – Chondrichthyes
Subclass – Elasmobranchii
Infraclass – Euselachii
Superorder – Selachimorpha
Order – Pristiophoriformes
Family – Pristiophoridae
Saw sharks have two genera:
- Pilotrema (Regan, 1906)
- Pristiophorus (J.P. Muller & Henle, 1837)
How to identify Sawsharks
Sawsharks resemble every other shark except for their long rostrum edged with sharp teeth. These sharks have two dorsal fins that are almost identical in size and a pair of long barbels (fleshy, slender, protuberances) near the midpoint of their snout. Saw sharks range from 28 inches (71 cm) to 54 inches (137 cm) in length, and they have brownish stripes on their snout. The females generally are on the larger side.
Sawsharks are usually yellowish-brown with spots, and they lack anal fins. These sharks have a large mouth with a row of small teeth and about 19 to 25 large teeth on each pair of barbels. Sawsharks navigate through the ocean using their barbells as an aid to detect prey in sand or mud.
Their long rostrum can also serve as a weapon against other predators. These sharks have sensory organs (ampullae of Lorenzini) covering them. As a sensory organ, they serve to detect electric field given off by potential prey even those buried in the sand.
Most Sawshark species occur in temperate waters at depths below 130 ft. The popular ones include the Longnose sawshark (Pristiophorus cirratus), and the Bahamas sawsharks (Pristiophorus schroeder).
Saw sharks species of the genus Pristiophorus have five pairs of gills slits while the three members of the Genus Pliotrema have six.
Their eyes are on the side of their head, and they also have spiracles. Sawshark has poor eyesight.
Side Note: Saw sharks have poor eyesight; therefore, they use their barbells and ampullae on the rostrum to detect prey instead of their eyes.
Distribution Range and Habitat
Sawsharks occur in the deep waters of Continental shelves of temperate, subtropical, and tropical oceans. They are common off the coasts of the Pacific oceans and the Indian ocean. Both the Southern Sawshark and the Common saw shark occurs in Australia’s southern temperate waters.
Tropical sawshark (Pristiophorus delicates) is endemic to tropical waters off northeastern Australia. Some species of saw sharks migrate up and down the water column in response to seasonal temperature fluctuations.
These sharks can be found in large schools, segregated according to age and size. Adult Sawsharks often swim to deeper waters compared to the juveniles. You can find some species of Sawsharks living at a depth of 131 to 328 feet (40 to 100 meters), while some, most notably the ones found in the Bahamas at a depth between 2,100 and 3000 feet (640 and 914 meters.)
Most sharks rely on water temperature to sustain the core of their body temperature. Responding to this, saw sharks migrate from the south during winter and to north during summer to keep their desired temperature range. They migrate using electroreception to reproduce and survive. Sharks give birth to pups in nurseries to keep them safe from predators.
Sawsharks are docile in nature. They do not pose any threats to humans except when captured or provoked. Nevertheless, they can inflict severe injuries when defending themselves by moving their saw from side-to-side.
Saw sharks are carnivores, that is, they feed only on flesh. Their diet consists of various types of small fish, squids, and crustaceans. These sharks sensory organs, called ampullae of Lorenzini, helps them to detect electric fields emitted by prey.
Sawsharks make use of their serrated snout to attack their victim. They swing their snout from side to side to cut the prey into fine chops that they can swallow easily. Some species of sawsharks are solitary hunters while others prefer to hunt in groups.
These amazing sharks have a slow life history. Their mating occurs seasonally in coastal areas. Sawsharks are ovoviviparous, i.e. eggs hatch inside the mother. These sharks produce about 3 to 22 pups every two years.
Their gestation period lasts for about 12 months. Thereafter, they give birth to live pups that are about 11 inches (30 cm) long at birth. While pups are in their mother, their teeth are inverted into their mouth to prevent them from harming the mother. Sawsharks are one of the few sharks that show parental care. Thus, they take care of their young ones for up to 2 years until they attain sexual maturity and can fend for themselves. Young sawsharks are born during winter.
Saw Sharks Size, Growth Rate, and Lifespan
Saw sharks grow to about 4.9 feet (1.5 meters) in length, depending on the species. Their females are a bit larger than the males, and they live about 15 years or more in the wild.
There is no estimate of the population trend or size of any sawshark. However, the International Union for Conservation Of Nature (IUCN) classifies the status of Sawsharks based on each species. Sixgill sawsharks are classified as “near threatened” while the tropical sawshark, common saw shark and southern sawshark are classified as “least concern.” There is no sufficient data to evaluate the status of the other species.
Large sharks like the great white shark, bull shark, and tiger shark are predators to Sawsharks.
These sharks prey on small sea creatures like shrimp, mollusks and crabs
Saw Sharks Interaction with Humans
Threats to Humans
Saw sharks are harmless to humans because of the depth at which they live. Thus, having very little or no chances of encountering humans.
These sharks are majorly fished for their delicious meat. They are famous for their thick and boneless flakes. Saw sharks have been commonly used for the traditional “Chips and Fish.”
Difference between Saw sharks and Sawfishes
People often confuse Sawsharks with sawfishes because of their similarities. They are the only cartilaginous fish possessing large saws. However, there is a difference between saw sharks and sawfishes.
Sawfishes are not sharks but a type of ray. While Sawfishes has gill slits positioned on the underside, sawsharks’ slits are on their side as an actual shark. One clear difference between Sawfish and saw shark is that sawfish lack barbells and sawsharks have prominent pairs of barbells halfway along with their saw. Sawshark barbells serve as a kind of antennae, feeling the way along the seafloor until it finds some prey of interest.
Both Sawfish and Sawshark use the electroreceptor on their saw, which is the ampullae of Lorenzini to detect the electric field given off by prey. The sawfish tend to grow much larger in size and have evenly sized teeth unlike the alternating teeth of the saw sharks.
Both Sawshark and sawfishes are widespread are around the world. Saw sharks are famous in tropical and subtropical waters of the Atlantic, western Pacific, and Indo-Pacific oceans. However, they are endemic in Australia. Meanwhile, Sawfishes prefers Coastal waters. They are both bottom dwellers, although Sawshark tends to keep too much deeper waters.
The main difference between Sawshark and Sawfishes is their size. Sawfishes are usually more significant in size than the saw sharks. They can grow over 20 feet and weigh over 1200 pounds. Saw sharks stay between the modest size of 5 feet and 19 pounds.
The Difference in Their Saw
The most visible difference between the saw of Sawsharks and that of Sawfishes is that the saw of the Sawfish have uniformly lined teeth that are equal in sizes, while saw sharks have teeth that are alternating between large and small. Also, Saw sharks have a wedge-shaped saw compared to the small rectangular saw of sawfishes. There is a single pair of barbs near the middle of their snout.
Both saw shark and sawfishes use their saw as a weapon. Their saws have a lot of sharp teeth which they use to bite their prey and undermine them, using fast lateral movement. Even more, saw sharks can use their saw to cut other fish into half.
Both saw shark and sawfishes have thousands of electroreceptors on their snouts. These sensors, which are called Ampullae of Lorenzini, are used as navigation to find prey.
Saw sharks like every other shark replace their teeth as they lose them, while sawfish teeth when they lose theirs, are lost forever
Difference in Species
There are five known species of sawfish which are Narrow, dwarf, small tooth, green sawfish, and largemouth. While on the other hand, there are ten species of saw sharks which are Kaja’s sixgill, Anna’s sixgill, warren’s sixgill, Shortnose, longnose, Tropical, Lana’s sawsharks, Japanese sawsharks, African dwarf sawshark, and Bahamas sawshark.
Difference in Fins
Saw sharks have a pair of pelvic fins, two spineless dorsal fins, unlike sawfishes whose pectoral fins are fused to their head.
Species of Saw Sharks
There are about ten known Species of saw sharks across the two genera in the family.
The genus Pristiophorus
- Common sawshark or Longnose sawshark – Pristiophorus cirratus
- Tropical sawshark – Pristiophorus delicatus
- Japanese sawshark – Pristiophorus japonicas
- African dwarf sawshark – Pristiophorus nancyae
- Bahamas sawshark – Pristiophorus schroeder
- Lana’s sawshark – Pristiophorus lanae
- Southern sawshark or Shortnose sawshark – Pristiophorus nudipinnis
The genus Pliotrema
- Kaja’s sixgill sawshark – Pliotrema kajae
- Anna’s sixgill sawshark – Pliotrema annae
- Warren’s sixgill sawshark – Pliotrema warreni
The first discovered sixgill sawshark is Warren’s sixgill sawshark (Pliotrema warreni). However, very recently (March 2020), two new species of sixgill sawsharks were discovered by looking at specimens in the local fisheries on the coast of Madagascar and Zanzibar. These new species include Kaja’s sixgill sawshark (Pliotrema kajae) and Anna’s sixgill sawshark (Pliotrema annae).
The sixgill sawsharks are extraordinary for their six pairs of gills located on the side close to the head. Warren’s sixgill sawsharks are usually pale brown and have a white underbelly. While the two new species are more yellowish than brown in color.
Apart from their color, their sizes also set them apart from the other species of saw sharks. Sixgill sharks are located around Madagascar and the southern part of South Africa. They usually occur in a depth range of 121.4 to 1, 640 feet (37 to 500 m), with preference to warmer water.
The females produce about 5 to 7 pups from eggs of 7 to 17. Six-gill Sawsharks keep their young in the range of 121.4 to 164 feet (37 to 50 m) to ensure they are warm. Their females are about 53.5 inches (136 cm) in size while their males are around 44.1 inches (112 cm). These sharks feed majorly on shrimps, squid and bony fish. The IUCN lists the Pliotrema warreni as “Near Threatened (NT)” on their Red List. For the other two new species, there is still so much to learn about them.
Longnose sawsharks (Pristiophorus cirratus) which is also the common Saw shark, is one of the eight species within the genus of Pristiophorus. They have unique characteristics that include their long thin and flat shape snout. In the middle of their snout, there are nasal barbels that protrude on both sides. Longnose saw sharks possess a pair of ampullae of Lorenzini and are unique among other species by having a longer snout.
These sharks are also not very big. Their length at birth is 14 inches while their length at maturity for males is 38 inches and 44 inches for females. These bottom-dwelling sharks also weigh about 18.7 pounds. Longnose sawsharks are endemic in Australia and can also be found in the eastern portion of the Indian ocean.
The longnose saw sharks prefer to swim at a depth range of 120 – 480 feet in both the coastal regions and the open sea. These sharks majorly feed on crustaceans, small teleost fish and small squids. They use their barbells to detect prey on the ocean floor which they then hit with the snout to immobilize the prey.
Longnose saw sharks have five gills on each side of their head and about 19 and 25 teeth on either side. Under the IUCN list, these sharks appear as “Least Concern (LC)”. The justification comes from the annual assessment of the current exploitation rate considered sustainable.
The tropical sawshark (Pristiophorus delicatus) is a species of saw shark that has a pale brown with a yellow hew coloration. They have an underbelly that is a pale yellow to white. These bottom-dwelling sharks live off the northeastern shore of Australia in depths of about 577.4 to 159.4 (176 to 405 m).
Apart from the location and appearance of these sharks, they are data deficient. It is tough to catch due to their ability to travel into ocean depths. Tropical sawsharks appear as “Least Concern (LC)” on IUCN Red List, therefore there are no conservation methods is in place for them.
The Japanese sawshark (Pristiophorus japonicas) is a species of saw sharks found in places like Korea, Japan, and northern China. They usually swim at a depth of 500 m.
Japanese sawsharks have around 15 to 26 large rostral teeth in front of their barbells that are equal distance from the gills to their snout. Also, they have about 9 to 17 teeth behind their barbells.
Like all other species of saw sharks, Japanese sawsharks are ovoviviparous, I.e. eggs hatch inside the mother. They feed on squids, crustaceans and all other small bottom-dwelling organisms.
The IUCN assessed this species as “Data Deficient (DD)”
Lana’s sawsharks (Pristiophorus lanae) are usually found in the philippine coast. They were discovered in 1966 by Lana Ebert, that identified them as a new species based on the number of their rostral teeth.
They earned their name after Lana Ebert graduated from the University of Francisco. These sharks have a dark uniform brown color on their dorsal side and pale white on their ventral side. Lana’s Sawsharks have a slender body and five gills on each side. They can grow up to around 70 cm.
African Dwarf Sawshark
African dwarf sawsharks (Pristiophorus nancyae) are small five-gill Sawsharks that can be found off the coast of Mozambique. They were first discovered in 2011 when a specimen was caught off the coast of Mozambique swimming at a depth of 1600 ft.
After that, the African dwarf has been spotted off the shores of Yemen and Kenya. They can be distinguished from other species by their location and their barbels closer to their mouth than the end of their rostrum.
These sharks are brownish greys in coloration and have white color along their ventral side. As a newly discovered species, African dwarf Sawsharks are also data deficient.
In the IUCN Red List, this shark is “Least Concern (LC)”. They are deepwater dwellers in areas without significant deepwater fisheries.
Southern or Shortnose Sawsharks
Southern Sawsharks (Pristiophorus nudipinnis) are similar to the longnose Sawsharks, but they have a compressed body and shorter, more narrow rostrum. They also have about 13 teeth in front of their barbels and six behind it.
Shortnose Sawsharks tend to be uniformly slate grey with no spots or markings on their dorsal side, while they are cream or pale white color on their ventral side. Their females reach around 49 in long, while the males reach around 43 in. Shortnose Sawsharks can live up to about 9 or more years in the wild.
Like other sawsharks, Shortnose saw sharks live a benthic lifestyle, therefore feed on benthic invertebrates. They use their barbels to detect life on the seafloor and then paralyzed the prey with their rostrum.
The species like other sawsharks are ovoviviparous, thus give birth to a litter of 7 to 14 pups every two years. They are mostly found on ocean floors off the coast of Australia. These sharks as assessed by the IUCN are of “Least Concern (LC)”. The assessment is due to the stability of catch rates over an extended period coupled with active management.
The Bahamas sawshark (Pristiophorus schroeder) is “Data Deficient (DD)” according to the IUCN. Research is underway to learn more about these sharks.
They occur in areas like Florida, Cuba, and the Bahamas where they earned their name. These sharks swim at a depth of 1,312 – 3,280 feet (400 – 1000 m). Further, their snout with teeth that look like a saw and their length serves as a means of identification.
There is a species of sawsharks commonly referred to as the Eastern sawshark (Pristiophorus peroniensis). These sharks occur off southeastern mainland Australia at depths of around 328 and 2,067 feet (100 and 630 m). They also reach a length of about 4.46 feet (1.36 m).
Before the description of these species of sawsharks in 2008, Eastern sawsharks were known as Pristiophorus sp. However, they are currently regarded as a synonym to Pristiophorus cirratus, with coloration being the only difference.
Interesting Facts About Sawsharks at a Glance
1. Exhibition of Sexual Dimorphism
Sawsharks can reach about 5 ft in length and weigh about 18.7 pounds in weight. In all, their females are slightly larger than males.
2. The Presence of Distinguished Dermal Denticles
Their body is covered with placoid scales called dermal denticles with pointed tops. Sawsharks have a yellowish-brown skin that is included with dark blotches and spots. This skin coloration serves as camouflage when they are in sandy bottoms.
3. They got their Name from the Saw-like Rostrum Protruding from the Snout
Sawsharks are famous because of their long rostrum that resembles a saw, hence how they got their name.
4. Sawsharks have Barbells in the Middle of their Snout
These sharks have a pair of barbells in the middle of their snout which is used as a sensory organ.
5. They Possess the Electroreceptor Ampullae of Lorenzini
Sawsharks used an organ called ampullae of Lorenzini to detect prey
6. Sawsharks Lack Anal Fins
Unlike most sharks, Saw sharks do not have anal fins. They have two dorsal fins.
7. These Sharks are Carnivorous
Sawsharks are carnivorous. Their diet consists of crustaceans, squids and small fishes.
8. They Exhibit both Social and Solitary Behaviors
Sawsharks can be part of a group or live as solitary creatures.
9. Reproduction Takes Two Years
Their mating season takes place seasonally in coastal areas. Though, the females are only able to reproduce every two years.
10. Females are Ovoviviparous
Sawsharks are ovoviviparous, that is, eggs hatch inside the female’s body after 12 months and the mother delivers up to 3 to 22 pups.
11. Pups are Born with Teeth Folded Against Their Snout
Pups of young sharks are born with folded teeth against their snout to prevent severe injuries to the mother during birth. More so, The pups emerge fully developed, looking like the miniature version of their mother.
12. These Sharks Exhibit Parental Care
Saw sharks are one of the few sharks that show parental control to their young ones until they are sexually matured and can feed for themselves.
- “Order Pristiophormes: Sawsharks”, ReefQuest Centre for Shark Research.
- “Two New Wonderfully Weird Species Of Six-Gilled Sawshark Have Been Discovered”, IFL Science.
- “Sawshark”, Wikipedia. (Accessed April 7, 2020).
- “Sawshark Facts: Pristiophormes”, ThoughtCo.