Sawfish are unique marine animals characterized by an elongated, flattened snout lined with sharp, tooth-like structures. These creatures, often mistaken for sharks due to their robust bodies, are actually members of the ray family. Their saw-like rostrum plays a central role in their survival and interaction with their environment.
Distinctive Anatomy and Function
The most recognizable feature of the sawfish is its long, flat rostrum, commonly referred to as a “saw.” This appendage is an extension of the animal’s cartilaginous skull, covered in skin. Along its edges are numerous structures resembling teeth, which are modified dermal denticles, not true teeth. These rostral teeth grow throughout the sawfish’s life but are not replaced if lost from the base.
The rostrum typically accounts for one-quarter to one-third of the sawfish’s total body length. It contains numerous sensory pores, known as ampullae of Lorenzini, which detect weak electrical fields produced by prey, even in murky waters. This sensory capability is crucial for hunting. The saw is used to slash through schools of fish, stunning or impaling them, and to dislodge crustaceans and mollusks from the seabed. It also serves as a defense mechanism against predators.
Sawfish possess a flattened body and head, with gill slits on their underside, distinguishing them from sharks whose gill slits are on their sides. They have two distinct dorsal fins, wing-like pectoral and pelvic fins, and a tail that provides propulsion. Sawfish can grow to be very large, with some species reaching lengths of up to 7.6 meters (25 feet) and weighing as much as 600 kilograms (1,323 pounds).
Ecology and Behavior
Sawfish inhabit a variety of environments, preferring shallow tropical and subtropical waters. They are commonly found in coastal marine areas, brackish estuaries, and can venture into freshwater rivers and lakes. This adaptability to varying salinities makes them euryhaline; some species, like the largetooth sawfish, demonstrate a notable affinity for freshwater habitats. They reside in waters less than 10 meters deep, over soft bottoms of mud or sand, and in areas with seagrass or mangroves.
These animals are bottom-dwellers that primarily feed on fish and crustaceans. Sawfish are known for their nocturnal hunting behavior. They use their distinctive rostrum in several ways to acquire food.
They may swing the saw rapidly through schools of fish, stunning or injuring them, making them easier to consume. The saw is also used to dig into the substrate, unearthing hidden prey such as invertebrates. After stunning or dislodging prey, sawfish consume them whole with their small mouths on their underside.
Sawfish reproduce relatively slowly. They are ovoviviparous, meaning eggs hatch inside the mother, giving birth to live pups. Litters typically range from 7 to 14 pups. At birth, young sawfish have a flexible saw encased in a gelatinous sheath to prevent injury to the mother, which dissolves shortly after birth. Sawfish can live for 25 to 30 years, reaching sexual maturity around 7 to 12 years of age, depending on the species.
Conservation Status
All five species of sawfish globally face a critical conservation status, listed as either Endangered or Critically Endangered by the International Union for Conservation of Nature (IUCN). Their populations have declined in recent decades, leading to their disappearance from much of their historical range.
A primary threat to sawfish is habitat loss. Coastal development and destruction of critical nursery habitats, such as mangrove forests and shallow estuaries, reduce areas where sawfish can breed and grow. Another major threat is accidental capture in fishing gear, known as bycatch. Their long, toothed rostrums easily become entangled in fishing nets and lines, making them vulnerable. Once entangled, sawfish are difficult to release without injury, and some are killed due to damage they can cause to fishing equipment or out of fear.
Targeted fishing for their saws also contributes to their decline. The rostrums are sometimes sold as curiosities or used in traditional medicine, and their fins are sought after for shark fin soup. International trade in sawfish and their parts is restricted under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix I. Conservation efforts include establishing protected areas, implementing regulations for safe release of accidentally caught sawfish, and raising public awareness about their plight.