Sawfish

Sawfish also known as carpenter sharks, are rays that have a long, thin, flattened rostrum, or nose extension, lined with sharp transverse teeth arranged in a sawlike pattern. They are among the world's largest fish, with some species exceeding 7–7.6 m (23–25 ft) in length. They can be found in tropical and subtropical climates, as well as freshwater rivers and lakes, in coastal marine and brackish estuarine waters. They are now in danger of extinction.

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Saw sharks (order Pristiophoriformes) and extinct sclerorhynchids (order Rajiformes) have a similar appearance, as do swordfish (family Xiphiidae), which have a similar name but a very different appearance. Sawfish are slow to reproduce, and females only give birth to live young. They eat fish and invertebrates that they detect and catch with the aid of their saw. They are normally harmless to humans, but when cornered and defending themselves, they can cause serious injuries with the saw.

For thousands of years, sawfish have been recognised and hunted, and they play a significant mythological and spiritual role in many cultures around the world. Sawfish, which were once abundant, have declined rapidly in recent years, with the only remaining strongholds in Northern Australia and Florida, USA. The IUCN has classified the five species as Endangered or Critically Endangered. Their fins (shark fin soup), pieces used in traditional medicine, teeth, and saw are all hunted. They are also threatened by habitat destruction. Since 2007, sawfish have been on the CITES list, which prohibits international trade in them and their parts. They are covered in Australia, the United States, and a number of other nations, which means that accidentally captured sawfish must be released, and violations will result in hefty fines.

Scientific Classification 

• Kingdom - Animalia 

• Phylum - Chordata

• Class - Chondrichthyes

• Order - Rhinopristiformes 

• Family - Pristidae

               Bonaparte

Appearance and Anatomy

Above, sawfish are dull brownish, greyish, greenish, or yellowish, but the colouration varies, and dark individuals may be nearly black. The underside is usually whitish and pale.

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Saw

The most distinguishing characteristic of sawfish is their saw-like rostrum, which is flanked on either side by a row of whitish teeth (rostral teeth). The rostrum is a cartilage and skin-covered extension of the chondrocranium ("skull"). The length of the rostrum is usually one-quarter to one-third of the total length of the fish, although it varies by species and, in some cases, by age and sex. The rostral teeth are highly modified dermal denticles, not teeth in the conventional sense. The sawfish's rostral teeth develop in size over time, and if a tooth is lost, it is not replaced.

Teeth can be found along the entire length of the rostrum in Pristis sawfish, but there are none on the basal one-quarter of the rostrum in adult Anoxypristis (about one-sixth in juvenile Anoxypristis). The number of teeth on each side of the rostrum varies by species and can vary from 14 to 37. It's not usual for a sawfish's rostrum to have slightly different tooth counts on each side (difference typically does not surpass three). Females in some species have fewer teeth on average than males. In Pristis sawfish, each tooth is peg-like, while in Anoxypristis, each tooth is flattened and broadly triangular. Usually, a combination of characteristics, such as fins and rostrum, are used to distinguish the species, but the rostrum can be used alone.

Head Body and Fins 

The body of the sawfish is sturdy and shark-like, with a smooth underside and a flat head. Because of the covering of dermal denticles, the skin of Pristis saw fish has a rough sandpaper-like texture, while the skin of Anoxypristis is largely smooth. On the underside of the head, the mouth and nostrils are located. In the upper jaw, there are approximately 88–128 small, blunt-edged teeth, and in the lower jaw, there are approximately 84–176 small, blunt-edged teeth (not to be confused with the teeth on the saw). 

On each jaw, these are arranged in 10–12 rows and resemble a cobblestone lane. They have tiny eyes and a spiracle behind each one that draws water past the gills. The location of the gill openings distinguishes them from saw sharks, which have slits on the side of the neck and are superficially similar but are much smaller (up to 1.5 m or 5 ft long). Saw sharks, unlike sawfish, have a pair of long barbels on their rostrum ("saw").

Sawfish have two distinct dorsal fins that are relatively high and distinct, wing-like pectoral and pelvic fins, and a tail with a distinct upper lobe and a variable-sized lower lobe (lower lobe relatively large in Anoxypristis; small to absent in Pristis saw fish). The first dorsal fin's location in relation to the pelvic fins differs, and it's a useful feature for distinguishing some organisms. Anal fins aren't there.

Sawfish, like other elasmobranchs, lack a swim bladder (instead of relying on a massive oil-rich liver to maintain buoyancy), have a cartilage skeleton, and males have claspers, a pair of elongated structures found on the underside of the pelvic fins that are used for mating. In young males, the claspers are tiny and indistinct. Their small intestines have an internal partition called a spiral valve that is shaped like a corkscrew and increases the surface area available for food absorption.

Size

Sawfish can grow to be very large, but the maximum size of each species is unknown. The world's largest fish are the smalltooth sawfish, large-tooth sawfish, and green sawfish. They can all grow to be about 6 m (20 ft) in length, and there have been reports of individuals growing to be greater than 7 m (23 ft), but these are also labelled with some doubt. The overall total lengths of these three are usually estimated to be between 7 and 7.6 m (23–25 ft). Individuals weighing 500–600 kg (1,102–1,323 lb) or more are considered high. There are old unconfirmed and highly dubious accounts of much larger individuals, including one with a length of 9.14 m (30 ft), another with a weight of 2,400 kg (5,300 lb), and a third with a length of 9.45 m (31 ft) and a weight of 2,591 kg (5,712 lb).

The dwarf and narrow sawfish, the two remaining species, are much smaller but still massive fish with overall total lengths of at least 3.2 m (10.5 ft) and 3.5 m (11.5 ft), respectively. The dwarf sawfish was once thought to only attain a maximum length of 1.4 m (4.6 ft), but this is now considered to be wrong.

Distribution Range 

Sawfish can be found in tropical and subtropical waters all over the world. They used to stretch from Morocco to South Africa in the East Atlantic, and from New York (United States) to Uruguay in the West Atlantic, including the Caribbean and Gulf of Mexico. Old accounts from the Mediterranean (the most recent in the late 1950s or shortly after) have been dismissed as vagrants, but a study of records strongly indicates that this sea had a breeding population. They ranged from Mazatlán (Mexico) to northern Peru in the East Pacific. While the Gulf of California has been included in their range on occasion, the only Pacific Mexican sawfish records are from south of the mouth. They were found all over the western and central Indo-Pacific, from South Africa to the Red Sea and the Persian Gulf, east and north to Korea and southern Japan, and south to Papua New Guinea and Australia. Sawfish have vanished from much of their historic range today.

Habitat

Sawfish are mainly found in coastal marine and estuarine brackish waters, but they are also found in freshwater and are euryhaline (can adapt to a variety of salinities). The large-tooth sawfish, also known as the freshwater sawfish, has a strong preference for freshwater. It has been seen as far as 1,340 kilometres (830 miles) up the Amazon River and in Lake Nicaragua, and its young spend their first years in freshwater. Smalltooth, orange, and dwarf sawfish, on the other hand, usually avoid pure freshwater, but they can sometimes migrate up rivers, particularly during periods of increased salinity. There have been records of narrow sawfish being seen well upriver, but these need to be confirmed and may be misidentified as other sawfish species.

Sawfish are often found in shallow waters, usually less than 10 m (33 ft) deep, and on rare occasions less than 1 m deep (3.3 ft). Young prefer shallow water and are often found in just 25 cm (10 in) deep water. Sawfish can be found off the coast, but they seldom go deeper than 100 metres (330 ft). At a depth of over 175 metres, an unidentified sawfish (either a large-tooth or small-tooth sawfish) was caught off the coast of Central America (575 ft).

Dwarf and large-tooth sawfish are warm-water species that prefer water temperatures of 25–32 °C (77–90 °F) and 24–32 °C (75–90 °F), respectively. Green and smalltooth sawfish can be found in colder waters, down to 16–18 °C (61–64 °F), as shown by their (original) ranges, which were further north and south than those of the strictly warm-water species. Sawfish are bottom-dwellers, but in captivity, at least the large-tooth and green sawfish have been seen eating from the water's surface. Sawfish are often found in areas with soft bottoms, such as mud or sand, but they can also be found near coral reefs or on hard rocky bottoms. They are mostly found in seagrass or mangrove habitats. Saw sharks are usually found much deeper than sawfish, often in excess of 200 metres (660 feet), and when found shallower, often in colder subtropical or temperate waters.

Breeding and Life Cycle of Saw Fish 

The reproductive habits of sawfish are poorly understood, but all species are ovoviviparous, with adult females giving birth to live young once or twice a year. Males tend to reach sexual maturity at a younger age and with smaller body size than females. Sexual maturity is achieved at 7–12 years in Pristis and 2–3 years in Anoxypristis, according to what is understood. This equates to a total length of 3.7–4.15 m (12.1–13.6 ft) in small-tooth and green sawfish, 2.8–3 m (9.2–9.8 ft) in large-tooth sawfish, 2.55–2.6 m (8.4–8.5 ft) in dwarf sawfish, and 2–2.25 m (6.6–7.4 ft) in narrow sawfish. This suggests that the narrow sawfish has a generation length of about 4.6 years and the remaining population has a generation length of 14.6–17.2 years.

To fertilise the eggs, the male inserts a clasper, which is organs at the pelvic fins, into the female. Mating tends to be rough in many elasmobranchs, with the sawfish often suffering lacerations from its partner's saw. However, genetic research has shown that at least the smalltooth sawfish can reproduce by parthenogenesis, in which no male is present and the offspring are identical to their mother. Parthenogenesis tends to be responsible for about 3% of smalltooth sawfish offspring in Florida, United States. It's thought that this is due to the females' inability to find a mate, causing them to reproduce anyway.

The pregnancy lasts a long time. Each sawfish litter has 1–23 young, which are 60–90 cm (2–3 ft) long when they are born. The rostrum is flexible in embryos and only hardens shortly before birth. The saws of the young have a softcover to shield the mother, which falls off shortly after birth. Coastal and estuarine waters are where the pups are born. The young of most species tend to remain there for the first few years of their lives, only moving upriver as the salinity rises. The large-tooth sawfish is an exception, as it’s young migrate upriver into freshwater, where they remain for 3–5 years, often as far as 400 kilometres (250 miles) from the sea. The young of the smalltooth sawfish demonstrate some site loyalty, remaining in the same relatively small area for the first part of their lives. There are signs that both sexes of green and dwarf sawfish remain in the same overall region throughout their lives, with little mixing between subpopulations. Males tend to travel more freely between subpopulations in large-tooth sawfish, while mothers return to the area where they were born to give birth to their own young.

The lifespan of sawfish is unknown. A green sawfish captured as a juvenile lived in captivity for 35 years, and a smalltooth sawfish lived in captivity for more than 42 years. The lifespan of the narrow sawfish is estimated to be about 9 years, while the lifespan of the Pristis sawfish is estimated to be somewhere between 30 and 50 years depending on the species.

Sawfish Feeding

Sawfish are predatory fish, crustaceans, and mollusc eaters. Sawfish attacks on large prey like whales and dolphins by cutting out bits of flesh are now considered legends rather than facts. Humans are much too big to be considered prey. They are usually fed ad libitum or in fixed quantities in captivity, which equals 1–4% of the total weight of the sawfish each week, but there is evidence that captives develop much faster than their wild counterparts.

The rostrum (saw) is unusual among jawed fish in that it plays an important role in both finding and catching prey. The ampullae of Lorenzini, which are found in the head and rostrum, enable the sawfish to detect and track the movements of other organisms by measuring the electric fields they emit. Other fish families have been shown to have electroreception. The sensory organs are most tightly packed on the upper and lower sides of the rostrum in sawfish, though there are small variations in their location and number depending on the species. Even in low-visibility waters, those on the upper side allow sawfish to create a three-dimensional view of the region above them. Sawfish can "view" their entire surroundings by remaining low to the seafloor and using their saw as an extended sensing system. From a distance of around 40 cm, sawfish tend to be able to identify possible prey items using electroreception (16 in). Some of the waters where sawfish live are very muddy, making sight hunting difficult.

It's been debated how they use their saw after they've found the prey, and some scholarship on the topic is focused on speculation rather than actual observations. In 2012, it was discovered that there are three main techniques: "saw in the water," "saw on the substrate," and "peg." If the sawfish encounters a prey object such as a fish in open water, it employs the first approach, slashing the prey with its saw to incapacitate it. It is then transported to the seabed and consumed. The "saw on the substrate" is similar, but it is used on seabed prey. The saw is very streamlined, causing very little water movement when swiped. The final technique involves pinning the prey to the seabed with the underside of the saw, similar to how guitarfish do it. 

The "pin" is often used to manipulate the prey's location, allowing fish to be swallowed head-first and thus avoid any potential fin spine engagement. Catfish spines have been discovered embedded in the rostrum of sawfish, a common prey. Mullet schools have been seen attempting to flee sawfish. Prey fish are usually eaten whole and not cut into small pieces with the saw, though the slashing motion can often break one in half during capture. As a result, prey selection is constrained by the size of the mouth. A 33 cm (13 in) catfish was found in the stomach of a 1.3 m (4.3 ft) sawfish.

The use of a sawfish saw to dig/rake in the bottom for prey has been proposed in the past, but this was not observed during the 2012 research or confirmed by subsequent hydrodynamic studies. The tips of the rostral teeth of large sawfish are often worn.

Sawfish Self-Defence 

Sawfish were once thought to be extremely dangerous to humans, sinking ships and slicing people in half, but these tales are now considered myths rather than facts. Sawfish are actually docile and harmless to humans, except when caught when they can cause severe injuries by thrashing the saw from side to side to protect themselves. The saw is also used in self-defence against predators that might consume sawfish, such as sharks. They have been seen in captivity using their saws during battles over hierarchy or food.

Interesting Facts About the Sawfish

Just looking at these creatures is interesting! Learn what else makes this group of species so unique below.

• What is the Saw? – First and foremost, what is the nature of this fish's saw? It's really a rostrum, or "nose," that has been changed. The saw's points are teeth that protrude from either side of the rostrum.

• What Does it Do? – They can use their spiky arms to defend themselves, but they often use them to aid in the capture of fish. This animal, like the swordfish, stuns schools of fish by swinging its rostrum back and forth. Then, since its mouth is located under its body like a stingray, it swims over top of the fish to feed!

• Speaking of Stingrays –This strange collection of fishes is directly linked to stingrays. Guitarfishes, shovelnose rays, banjo rays, and wedgefishes are their nearest relatives. Researchers, on the other hand, place them in the same superorder as rays and the same class as sharks!

• Sawshark – Researchers group Sawsharks with the sharks and Sawfish with the rays, despite the fact that another group of shark family fish looks strikingly similar to the Sawfish. Saw sharks are typically smaller than their ray-like relatives.

Conclusion 

Sawfish are similar to sharks and belong to the Rajiformes order, which includes flattened marine fish such as rays and skates. In this article, there is a brief explanation about sawfish, like scientific classification, Distribution range, habitat, breeding life cycle, appearance and habitat. Sawfish have developed a long snout with unique teeth, unlike the majority of the cartilaginous fishes. The rostrum, or saw-like snout, can be used in a back-and-forth swiping motion to cut prey in half or dig through sediment.