(Pacific) Largetooth Sawfish
Saw fish look somewhat like sharks, except for their long, toothed rostrum (snouts), but they are modified rays. The 'teeth' on their rostrum are specialized denticles, a type of scales, and they stun or impale small fish by thrashing their rostrum from side to side. They prefer living in shallow inshore areas in the eastern Pacific, and swim up rivers into freshwater periodically, where they can feed on small fish and other bottom-dwelling prey. These sawfish usually grow to over 20 feet long, but are only a danger to humans when startled or threatened because of their size and defense response.
Order - Pristiformes
Family - Pristidae
Genus - Pristis
Species - zephyreus
English language common names for this species are largetooth sawfish, large-tooth sawfish, southern sawfish, common sawfish, freshwater sawfish, sawfish, and saw fish. Other common names include stortandet savrokke (Danish), billi sovulu, chakku thatte, naithatte (Kannada), makara sravu, vala sravu, velli sravi (Malayalam), hachutti meenu, shinesi (Telugu), iluppa, vela (Tamil), catanuda, pez espada, pez peine, pez rastrillo, pez sierra, sierra (Spanish), araguagua, peixe-serra (Portuguese), zaagvis, groottandzaagrog (Dutch), krarien, and sartji (Sranan).
Importance to Humans
Sawfish are frequently harvested for their meat, fins and saws, liver oil and skin; liver oil, eggs and bile from sawfish are used in traditional Asian medicine. Ancient paintings suggest that saws were used in religious ceremonies or as offerings in Aboriginal, African, and Asian cultures. Sawfish are also prize game in reel and rod fishing for their size, power, and agility.
Danger to Humans
Sawfish pose no threat to humans; while occasionally caught on lines, it is important to note to be careful when handling and releasing the animal so that no injury results. Sawfish will use their rostrum when they feel threatened, thrashing in a side-to-side motion to defend themselves.
P. zephyreus are listed as endangered under the ICUN Red List, as well as Appendix I of the Convention on the International Trade of Endangered Species (CITES). However, human impact has dramatically lowered sawfish populations by becoming by-catch in gillnet fishing, getting caught in discarded fishing line and nets, pollution runoff and illegal harvesting. Current population estimates are not available and very little is known concerning this species.
The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.
Geographical DistributionZephyreus is taken from the Greek zephuriois, meaning "of the west" or "west-wind" as this species is believed to have originated on the western shores of South America. It is found in the eastern Pacific Ocean, residing in coastal waters from the Gulf of California to the northern shores of Peru.
Sawfish are commonly found in shallow, coast water that tends to be murky and muddy in nature. Sawfish also seem to frequent coastal estuaries and even some freshwater systems. However, the exact habitat of P. zephyreus is not well known; however it is interesting to note that each largetooth species originated in different areas: P. microdon from the Indo-West Pacific, P. perotteti from the Atlantic, and P. zephyreus from the Eastern Pacific.
Although P. zephyreus is often mistaken for other large tooth species as they are all very similar morphologically, there are some defining characteristics of the species. In general, P. zephyreus tends to have greater variation in rostral tooth count (or the teeth that line the elongated snout of the sawfish). The distance between the nostrils and the length of the lower lobe of the claudal fin also tend to differ from that of other species.
This species also has a robust rostrum and rostral tooth count varies between males and females, males having a higher average of teeth. There is also a difference in the spacing of the back two rostral teeth, females using having a larger gap. Rostral tooth count per side usually ranges between 15 and 23.
In order to camouflage into their environment, sawfish usually have a light tan or brown sheen on their dorsal surface to blend into the muddy water they inhabit. The ventral side is usually creamy variation of yellow or a dirty white to help blend in to the bright surface water.
Sawfish are often described as a mix between a shark and a ray, their mouths following suit with those of a ray. Two crushing plates, one lower and one upper jaw lined with rounded cusps, aid in feeding on the hard shells of prey and crush in a rolling motion.
Sawfish are covered in tiny tooth-like skin cells called dermal denticles. These arrow head shaped ridges do not fully appear on the entire body of the animal until all of the rostral teeth have appeared.
Size, Age, and Growth
Maximum size of P. perotteti has been reported between 20.0-21.2 feet(6.1-6.5 m) total length and between 1,102-1,323 pounds (500-600 kg) The maximum total length of juveniles was recorded to be 940 mm as measured for a female from Rio Tuyra, Darien, Panama. For adults, total length is thought to range from 14.8-19.7 feet inches (450-600 cm). Females are also generally larger in size than the males.
While the exact diet of P. zephyreus is not known, based on their composition as a bottom feeder (their mouths are located on the bottoms of their bodies), it is safe to assume they feed on prey that inhabits the bottoms of shallow waters. The rostrum is also used in a back and forth motion to stun prey for consumption. Hard crushing plates within the mouth also aid in breaking shells of prey.
Sawfish reproduce sexually through internal fertilization; they are also considered viviparous meaning the embryo feeds on the yolk sac until completely developed, after which the mother gives live birth.
While no known natural predators exist for adult sawfish, younger and smaller sawfish can fall victim to large sharks and saltwater crocodiles. Marine debris from human use, such as discarded fishing line and nets, also account for sawfish fatalities.
While not considered a parasite itself, remoras are frequently seen attached to sawfish; this symbiotic relation offers relief to the sawfish of parasites as the remora helps remove them, and the remora will feed off of bits of food that break off while the sawfish is feeding.
Although John Latham composed an essay on the types of sawfish in 1794, he was unable to fully name and describe P. zephyreus. It wasn't until Jordan and Starks described the species in 1895 that it was finally possible to classify the species. P. zephyreus first emerged as a species when morphological differences were noticed between P. perotteti and other museum specimens. As more research began to emerge, P. zephyreus was often times lumped together or often mistaken for other largetooth species, usually either P. perotteti or P. pristis. In 1905 H. Fowler composed a subgenusPristiopsis for sawfish that had a lower lobe claudal fin, in which the largetooth species (including P. zephyreus, P. microdon, P. perotteti, and P. antiquorum were included) as well as P.cuspidatus (or A. cuspidata). The largetooth group of sawfish now includes P. microdon, P. perotteti, and P. zephyreus.
Prepared by: Ashley Hechavarria