Green SawfishPristis zijsron
Sawfish look a lot like sharks, but their flattened bodies and wide pectoral fins reveal that they are actually rays. Their unusual snouts (rostrum) are studded with denticles, specialized scales, instead of teeth. They do have rows of small rounded teeth in their mouths for crunching on small bony fish and invertebrates, which they often stun by thrashing their rostrum side to side along the muddy floors of bays and estuaries. These sawfish grow to around 24 feet long, easily the largest sawfish species, and their rostrum can get to be over 5 feet long.
Order - Pristiformes
Family - Pristidae
Genus - Pristis
Species - zijsron
Common English names used for the green sawfish include longcomb sawfish, longsnout sawfish, narrowsnout sawfish, narrow-snouted sawfish, and sawfish. These names refer to the exceptionally long and slender rostrum of this species. Other language names for this species include: abusef, sayyaf, and sayyafah (Arabic), dindagubba (northern Australia Aboriginal), groene zaagrog (Dutch), grøn savrokke (Danish), langkam-saagvis (Afrikaans), requin scie (French), tubarão-serra africano (Portuguese), vella-sorrah and vezha (Tamil), and yubadhi (Guugu Yimidhirr).
Importance to HumansLandings of the green sawfish are usually accidental, as they are caught in prawn trawlers, as well as in inshore gill nets targeting barramundi (Lates calcarifer) and threadfins (Polynemidae) in the Gulf of Carpentaria, Australia. This species may occasionally be targeted in directed fisheries in parts of its range. This species is sometimes used for human consumption in northern Australia, where it is marketed as fried fish. Like all sawfishes, green sawfish fins can be sold into the Asian 'shark fin' market, their livers can be processed for oil, and their skins can be made into leather. In addition, the eggs, liver oil, and bile of sawfishes can be used in Chinese traditional medicine. Also, like all other sawfishes, their rostra may be used in traditional medicine, as religious offerings, and sold as curios. In addition to these uses of the green sawfish, Australian Aboriginals sometimes depict sawfishes such as this species in their bark paintings, suggesting that sawfishes hold significant meaning to them.
There is little indication of this species being sought after as a game fish using rod and reel, although this species may sometimes be landed in Queensland fishing tournaments. Although large green sawfish are capable of long and stubborn fights even on heavy tackle, this species lacks the aerial acrobatics and swiftness that adds to the appeal of more typical game fish. The International Game Fish Association does not have a record holder for the green sawfish.
Danger to Humans
The green sawfish is, like all sawfishes, harmless to humans if left undisturbed. Humans are too large to be viewed as potential prey. Care must be taken when handling or approaching a sawfish of any size, as they may defend themselves when they feel threatened, using their rostrum to strike from side-to-side with considerable force. The green sawfish attains a large size and is equipped with a long rostrum sporting numerous laterally projecting sharp teeth, and for these reasons extra care should be afforded when encountering this species.
The status of the green sawfish populations is currently unknown, and no effective legislation exists to protect this species. However, The World Conservation Union (IUCN) Red List of Threatened Species categorizes this species as "Critically Endangered". It is thought to have experienced significant population decline in many parts of its range. This species is vulnerable as bycatch in nearshore trawl and gillnet fisheries. In addition, hook and line fisheries may have significantly impacted the green sawfish, as the meat, fins, and rostra can be marketed. In northern Australia, this species is particularly vulnerable as bycatch in fisheries targeting barramundi (Lates calcarifer) and threadfins (Polynemidae), and it may sometimes be landed in Queensland fishing tournaments. It is caught accidentally in Natal and Durban (South Africa) anti-shark nets. Other impacts likely include human-induced habitat modification and pollution of inshore coastal waters, estuaries, and river systems.
Geographical DistributionThe green sawfish appears to be confined to the Indian and western Pacific oceans, although the precise range in this vast area is not clear. In Africa, the species is often confused with the similar-looking smalltooth sawfish (Pristis pectinata). The green sawfish occurs along the eastern African coastline from South Africa, ranging north along the east coast through Somalia and the Gulf of Aden to as far north as the Red Sea. It probably does not occur in the Mediterranean Sea. From the Gulf of Aden it ranges east along the Indian coast to Thailand and south through Indonesia. In Australia it occurs from Broome (Western Australia) to Sydney (New South Wales), and a single record exists from off Glenelg in South Australia. The green sawfish occurs off southern China and Vietnam in the South China Sea, throughout the Philippines, south through Borneo and east to Papua New Guinea. The green sawfish no longer appears to be common anywhere in its range.
This species lives close to shore in marine and estuarine waters throughout its range, and sometimes inhabits river systems in freshwater conditions. In the Gulf of Carpentaria, Australia, green sawfish prefer sand and mud substrates located outside of river mouths. The green sawfish is known to occur in freshwater in Indonesia including Borneo, Java, and Ternate; in Australia including the Gilbert and Walsh rivers; and possibly inland Thailand. It has been recorded in the Northern Territory of Australia more than 241.4 km (150 miles) from the sea. Depth preferences of this species are confined to about 5.0 m (16.4 feet) of water or less, although it may occasionally be found in deeper water and in the open sea.
All sawfishes are highly modified and elongate rays having a shark-like body and a blade-like snout (termed 'rostrum') that has lateral, tooth-like denticles (termed 'rostral teeth') set into sockets. The presence of a rostrum having laterally protruding teeth separates sawfishes from all other skates and rays.
The green sawfish can be distinguished from sawsharks (Pristiophorus spp.) by its lack of barbels, its body being dorso-laterally compressed, its ventrally located gills (not laterally), its similarly-sized rostral teeth, its large size, and its preference for shallow coastal habitats.
Due to its very large size, the green sawfish has perhaps the longest rostrum of any living species of sawfish, ranging to at least 1.66 m (5.4 ft) rostral length. The rostral tooth count for green sawfish varies between 23 and 37 (typically 25-34) per side. The rostral teeth often number more on one side of the rostrum than the opposing side.
The green sawfish is distinguished from the knifetooth sawfish (Anoxypristis cuspidata) by its sharply pointed rostral teeth (versus blade-like), greater number of rostral teeth per side (23-37 versus 18-25), presence of dermal denticles over the entire body, and the lack of a developed lower caudal fin lobe.
The green sawfish is distinguished from the dwarf sawfish (Pristis clavata) by its narrow-based and moderately tapering rostrum (versus wide-based and strongly tapering), greater number of rostral teeth per side (23-37 versus 18-23), and the lack of a developed lower caudal fin lobe. In addition, the green sawfish reaches a larger maximum size (7.3 m or larger versus 3.1 m total length) than does the dwarf sawfish.
The green sawfish looks most similar to the smalltooth sawfish (Pristis pectinata), but is distinguished from this species by the origin of the first dorsal fin positioned slightly posterior to the origin of the pelvic fins (versus directly over or slightly anterior to the pelvic fins), the space between last two rostral teeth on a side about 4-8 times the space between the first two teeth (versus 2-4 times), and the narrow and slightly less tapering rostrum. In addition, the green sawfish tends to have a greater average number of rostral teeth per side than that of the smalltooth sawfish, and often has a greenish body color (versus brownish or bluish-gray body color) when alive or fresh-dead. Rostra of very young green sawfish are very similar to that of the smalltooth sawfish, but whole specimens may be distinguished based on the positioning of the first dorsal fin slightly posterior to the origin of the pelvic fins (versus directly over or slightly anterior to the pelvic fins).
The green sawfish is distinguished from the largetooth sawfish (Pristis perotteti) by its geographic range (Indian and western Pacific oceans versus the western central Atlantic and eastern Pacific oceans). In addition, the green sawfish is distinguished from this species by the greater number of rostral teeth per side (23-37 versus 14-23), narrow-based and moderately tapering rostrum (versus wide-based and strongly tapering), the position of the first dorsal fin origin slightly posterior to that of the pectoral fins, the absence of a lower caudal fin lobe, and the comparatively slender build and lighter weight of the green sawfish.
The green sawfish is distinguished from the freshwater sawfish (Pristis microdon) by the same characteristics as the largetooth sawfish, except by geographic range. In addition, the green sawfish is much less frequently found in freshwater habitats than is the freshwater sawfish.
The dorsal surface of the green sawfish is colored greenish-brown or olive. Their rostral teeth are typically a dirty cream or yellow color, contrasting with the darker hue of the dorsal rostral surface. The eyes are gray to silver with black pupils. The dorsal fins are a dirty yellowish-gray. The lateral sides of this species are yellowish in color. The ventral surface of the body is colored a creamy white.
Green sawfish have many rows of very small oral teeth with rounded cusps that are close-set. Teeth are similar in both jaws. Most of the oral teeth are functional at the same time, and may show wear from use.
Dermal denticles of the green sawfish cover the body, fins, and rostrum. These denticles have a flat, oval-shaped or rounded crown and are similar in all development stages, although larger individuals exhibit a more pronounced crown than do young. Denticles along the posterior portion of the body are more elongate and convex. Denticles along the ventral body surface are smaller and are positioned in a pavement-like pattern. A mid-dorsal keel, composed of large specialized dermal denticles, extends from just beyond the spiracles to the base of the second dorsal fin. This dorsal keel appears darkly colored in fetal green sawfish.
Size, Age & Growth
This species attains a maximum size of at least 7.3 m (24.0 ft) total length. The green sawfish appears to grow longer than any other living sawfish species. Age and growth data has not been reported for this species. Males reach maturity at less than 4.3 m (14.1 ft). A post-partum female green sawfish measured 3.8 m (12.5 ft), recorded from the Gulf of Carpentaria (Australia).
Despite the green sawfish's interesting mode of food gathering, using its rostrum in a side-to-side slashing motion to dislodge invertebrates from substrate and to stun schooling fishes, little is known about the feeding habits of this species. Prey items of the green sawfish have not been reported, but likely include small schooling fishes, squids, and crustaceans such as crabs and shrimps.
Green sawfish, like all sharks, skates, and rays, have internal fertilization. This species, like all sawfishes, utilizes a strategy of embryo nourishment called aplacental yolk sac viviparity. With this strategy, the embryos are nourished only by their yolk sac, which provides energy for them to develop into fully functional young sawfish in utero. The embryos are nourished by yolk stored in a yolk sac, connected to the embryo by a yolk stalk and both of these structures are fully absorbed before the young sawfish are born.
The minimum length at maturity for male and female green sawfish has not been established. Males reach maturity at less than 4.3 m (14.1 ft) total length. A post-partum female green sawfish measuring 3.8 m (12.5 ft) has been recorded from the Gulf of Carpentaria (Australia). Parturition is thought to occur during the wet season (December-March) in the Northern Territory (Australia). The gestation period of the green sawfish is not known, but the largetooth sawfish has a gestation period of about five months, and may only give birth every other year. No information is available on litter sizes, but other sawfishes have litters of between 6 and 23 young. Green sawfish measure about 60-108 cm (24-43 inches) at birth and are probably born tail-first. The saw teeth of young sawfish do not fully erupt, and are also covered in a sheath of tissue, until after birth so as not to injure the mother. Young green sawfish rostral teeth reach their full size proportionate to the size of the rostrum soon after birth.
Although adult green sawfish have little or no natural enemies, part of a large specimen was found in the stomach of a 3.0 m (10 ft) total length tiger shark (Galeocerdo cuvier) caught in the Great Barrier Reef. Other predators of the green sawfish may include bull sharks (Carcharhinus leucas), and saltwater crocodiles (Crocodylus porosus). When entangled in nets, this species is vulnerable to predation.
The parasites Nonacotyle pristis, Neoheterocotyle darwinensis, and Pristonchocotyle papuensis (Hexabothriidae) inhabit the gills of other sawfishes off Darwin, Australia and in Papua New Guinea; and may also use the green sawfish as a host. The copepod Ergasilus sp. (Ergasilidae) inhabits the gills of the freshwater sawfish in the Daly River (Australia), and may also use the green sawfish as a host. This copepod also inhabits the barramundi (Lates calcarifer), which may be its primary host. Other species that may use the green sawfish as a host include monogenean helminths such as Erpocotyle caribbensis and Pristonchocotyle intermedia. These parasites inhabit the gills of the largetooth sawfish in Central America. The cestode helminths Phyllobothrium pristis andAnthobothrium pristis inhabit the spiral valve of the largetooth sawfish in Central America, and may also inhabit the green sawfish. Other likely parasites include nematodes, protozoans, and trematodes. Likely areas of parasite inhabitation include the skin, gills, and digestive tract. The effects of these parasites on the green sawfish are unknown.
In captivity, the green sawfish is susceptible to heavy infestations of trematodes, which can cover the body and cause apparent discomfort to the sawfish. Control of trematodes has been successful by introducing a small number of pennant coralfish (Heniochus acuminatus) to the aquarium. These fish prey on the flatworms and significantly control their numbers.
The green sawfish was first described by the industrious European ichthyologist Pieter Bleeker in 1851 while residing in Java. Bleeker lived in the East Indies for nearly two decades, which enabled him to collect and describe roughly 1,300 fishes of Indonesia, including the green sawfish. A rostrum measuring 99.1 cm (39 inches) long was taken from a specimen captured in a Borneo river and saved as an example of the species (termed 'type specimen'). This rostrum is currently housed at the Nationaal Natuurhistorische Museum in Leiden, Netherlands. The valid scientific name of the green sawfish is Pristis zijsron Bleeker, 1851. Synonyms for the green sawfish include a misidentification (Pristis pectinataLatham, 1794), an invalid species (Pristis leptodon Duméril, 1865), and several misspellings (Pristis zisron Bleeker, 1851, Pristis zyrson Bleeker, 1851, and Pristis zysross Bleeker, 1851). The generic name Pristis is Greek for "saw". It is unclear as to what the specific name zijsron was derived from, and it does not appear to be named after a person or a place. The suffix -on is Greek, however the remainder of the specific name zijsron does not appear Greek. The derivation of the name zijsron continues to be a mystery.
Prepared by: Jason C. Seitz