Author: Bleeker, 1859
Field Marks:
Long, flat snout with lateral sawteeth and ventral barbels, two spineless dorsal fins and no anal fin.
Habitat, Distribution and Biology:
Sawsharks are little-known temperate and tropical benthic and epibenthic inhabitants of the continental and insular shelves and upper slopes from close inshore to at least 915 m depth. Temperate sawsharks are found in shallow bays and estuaries down to offshore sand and gravel banks at modest depths, but one tropical species is a deepwater slope inhabitant at 640 m and below. The sawshark family is presently confined to the western North Atlantic in the vicinity of the Bahamas, the southeastern Atlantic and western Indian Ocean from the western Cape, South Africa, to southern Mozambique, apparently the Arabian Sea (where an undescribed species may occur), and the western Pacific off Japan, the Koreas, China, the Philippines and Australia. Fossil finds indicate that sawsharks were formerly more widespread, in the eastern Pacific and eastern North Atlantic.
Sawsharks are small and very slender, with a maximum total length of about 137 cm.
Several sawsharks are abundant where they occur, and are found in large schools or feeding aggregations. Despite their abundance, their habits are poorly known. At least one species shows segregation by depth within populations, with adults in deeper water than young.
Sawsharks are ovoviviparous, and may have litters of 7 to 17 large young that are 28 to 35 cm long at birth. Apparently sawshark fetuses gain nutrients primarily from their large yolk sacks, which are resorbed just before birth. Apparently the large lateral rostral teeth erupt before birth in sawsharks, but to prevent injury to the mother these large teeth lie flat against the rostrum in fetuses until after birth. Smaller teeth erupt between the large ones after birth.
Food habits of sawsharks are poorly known, but their prey includes small fishes, crustaceans and squids. The long rostral barbels may have taste sensors, that these sharks trail along the bottom like those of sturgeons (Acipenseridae) and catfishes (Siluriformes) to locate prey. The long, rather delicate rostrum has lateral line and ampullal sensors for vibration and electrolocation, like a paddlefish (Polyodontidae) snout. The lateral rostral teeth, flat snout and head, enlarged occipital condyles, and specialized cervical vertebrae of sawsharks are evident modifications that allow these sharks to use their rostra as offensive weapons to kill their prey and possibly stir up bottom sediments to rouse prey organisms, but unlike the batoid sawfishes (Pristidae) this behaviour has not been observed, probably because sawsharks apparently have not been kept in captivity with any success (unlike sawfishes) and have not been studied underwater where they occur. The very short jaws and long oral and gill cavities of sawsharks suggest that they are capable of suddenly sucking prey into their mouths.
Because of their small size and small, cuspidate teeth sawsharks are considered to be inoffensive to people (unlike large sawfishes which have occasionally injured and even killed bathers and may be a hazard to fishermen when caught in nets and on line gear). The rostral teeth of sawsharks are sharp as needles though apparently nontoxic, so that these fishes should be handled with care to prevent puncture wounds on one's limbs.
Interest to Fisheries:
Considerable fisheries for sawsharks have occurred off southern Australia. They are taken and used in the western North Pacific to some extent, but details are sketchy. Sawsharks are commonly taken in the southwestern Indian Ocean off South Africa and southern Mozambique, but may be little utilized there. Sawsharks are caught in bottom trawls, and used fresh for human consumption.
Remarks:
Arrangement of this family follows Springer and Bullis (1959).