Sawfish (Pristidae) are a family of five extant species of rays. Also called carpenter sharks, they are famous for their long flat rostra, which look like saws because of their sharp, evenly spaced teeth. Even though they look like saws, they aren’t used for chopping. And even though sawfish look like sharks, they aren’t sharks at all. Human activity has rendered all five species endangered or critically endangered, but humans once revered them.
1. The sawfish has a long snout called a rostrum with 20-37 teeth on each side
The sawfish received its common name in honor of its long, saw-like snout. This snout is called the rostrum. The rostrum is an extension of the fish’s skull. It usually makes up 20-30% of the animal’s length. The rostrum is also lined with an equal number of teeth on each side. These teeth are also evenly spaced. One sawfish can have anywhere from 20-37 teeth on each side.
The green sawfish has the longest rostrum out of all living species. Its blade can be ⅓ of its total body length
Out of all five living sawfish species, the green sawfish has the longest rostrum. Today, they grow to about 6m (20ft) long. But their rostrum can account for 33%, or ⅓, of its total body length. So if a green carpenter shark is 20ft long, its snout will be 2m (6’6”) long! Because this ray has such a long snout, it is also called the longcomb sawfish. But you wouldn’t want one to comb your hair.
2. Sawfish swing the rostrum in a school of fish to incapacitate prey, which they swallow whole
Carpenter sharks use their rostrum to stun or kill prey, which it swallows whole. A hungry carpenter shark will swing the rostrum into a school of fish, and eat the stunned fish. Sometimes, they cut fish in half, but this is not intentional. The rapid slash of the rostrum causes very little movement in the water, which means fish get cut in half a lot. Other times, carpenter sharks will use the saw to pin prey down before swallowing it.
3. The teeth are actually modified scales, and they will not grow back if they break off of their base
Even though the rostrum is part of the skull, a carpenter shark’s teeth are not made of bone. Their teeth are actually scales. They are modified forms of scales called dermal denticles, which are like a fish’s armour. These teeth grow for the ray’s entire life. But they do not grow back if they break off at the base.
4. The rostrum has electroreceptors called ampullae de Lorenzini, which detect electrical fields from prey
The rostrum is covered in small pores called ampullae de Lorenzini. These pores contain electroreceptors. The sawfish waves its rostrum over the ocean’s muddy or sandy bottom to detect prey. All animals, even humans, give off very tiny electric fields as their hearts beat. The rostrum detects the electric fields of prey hiding on the ocean floor.
5. Sawfish look like sharks, but are actually rays. Like the stingray, their pectoral and pelvic fins look like broad, flat wings
Despite the nickname carpenter sharks, sawfish are not sharks at all. They are actually rays. If you look at a carpenter shark as it swims around, it looks a lot like a shark. But if you look at one from below, you’ll see that it looks a lot like a stingray. Like stingrays, sawfish have broad but flat looking pectoral and pelvic fins.
As rays, sawfish have gills on their underside, but sawsharks have gills on their sides.
There is a species of shark called the sawshark. It also has a very long, toothed rostrum. It’s easy to get a saw shark and sawfish mixed up. But there’s also an easy way to tell the difference. The sawfish is a ray, so its gills are on its underside. They have five gill slits at the base of each pectoral fin. The saw shark is a shark, so its gills are on the sides of its body.
6. The gestation period for the smalltooth sawfish is 12 months
Sawfish are ovoviviparous. This means that the fertilized eggs hatch inside the mother. The embryos develop inside of her until the babies are ready to be born. For smalltooth sawfish, this process takes quite a while. The gestation period for smalltooths is 12 months, an entire year. Because of this, they only reproduce every two years. But mothers give birth to up to 20 pups at once.
When sawfish embryos develop, their teeth are covered in tissue so the babies don’t hurt the mother or each other
Sawfish are born with all the teeth their rostrum will ever have. The teeth develop when the ray is still an embryo in his mother’s uterus. Luckily, embryo teeth are covered in a protective layer of tissue. This way, the babies won’t hurt their mother as they are born. This tissue dissolves about two weeks after the pups are born.
7. Smalltooth sawfish can reproduce asexually don’t always need their eggs fertilized to reproduce
In one Florida estuary, 3% of the smalltooth population developed from unfertilized eggs. When unfertilized eggs develop into embryos, it is called pathogenesis. Females of the species are practicing facultative parthenogenesis, because they can reproduce sexually as well. Scientists speculate that female sawfish use facultative pathogenesis because habitat loss and population decline has made it harder for them to find mates.
8. Largetooth sawfish look red in freshwater because of blood diffusion
Largetooth sawfish are one of the very few sharks and rays that occur in both fresh and saltwater. To survive in saltwater, sharks and rays have to diffuse just the right amount of salt and nitrogen from their blood, while taking in a lot of water. Largetooth sawfish can alter their blood chemistry to their environment. This process causes the sawfish to look slightly red in freshwater. The blood just under its skin is quickly changing.
9. Sawfish in the wild are calm, and do not attack humans. But they can gravely injure humans trying to reel them in by violently slashing their rostrum.
Divers say that as long as they leave sawfish alone, they are calm and do not attack. But fishermen put themselves in grave danger. In addition to gravely hurting the fish, the fish can hurt them too. Sawfish caught on lines are known to start violently slashing their rostrum to escape, which can leave a nearby human with a grisly cut.
10. The Anindilyakwa People of Australia revered sawfish for their connection to Earth’s creation
Sawfish were honored in many different native cultures. The Anindilyakwa People of modern Australia believed that a mystical ancestor of the sawfish used its rostrum to carve out rivers and landscapes. That ancestor gave the land to humans before disappearing. So the humans respected its mortal descendant, the sawfish. To the Anindilyakwa, carpenter shark is an apt nickname, as they helped build the world.
Carpenter shark or metal detector shark?
Sawfish don’t use their saw the way a human uses a saw, so why are they compared to carpenters? If anything, rostrums are more like metal detectors. Metal detectors work by sensing electromagnetic fields that buried metals give off. Rostrums work the same way. Sawfish hover their rostrum over the ocean’s muddy bottom, until they detect a heartbeat. Then, they dig in. But “metal detector shark” doesn’t have the same ring to it, now does it?
How endangered is this animal?
- IUCN Status: Endangered/Critically Endangered
Endangered: Narrow sawfish & dwarf sawfish
Critically Endangered: Smalltooth sawfish, green sawfish, & largetooth sawfish
- Habitat degradation is the biggest threat to sawfish
Some species have lost 80% of their natural habitats
- Sawfish are common bycatches for commercial fisheries. Sawfish trapped in nets often thrash their rostrums to escape. Fishermen consider them pests and often kill them.
Also Known As
7–7.6 m (23–25 ft)
Worldwide in tropical and subtropical regions
Coastal marine and brackish estuarine waters
Fish, crustaceans and molluscs
Up to 35 years