When approaching maturity, subadults migrate back downstream to coastal waters, and mature at about 7 years of age. Pups migrate upstream and spend their first 4-5 years in freshwater river systems - as far as 400 kms upstream in the Fitzroy River, Western Australia. Sawfish are aplacental viviparous (ovoviviparous) meaning that the eggs hatch within the body of the female who gives birth to 1-12 young in estuaries. Sawfish - pups and small juveniles - are preyed upon by Bull Sharks ( Carcharhinus leucas), estuarine crocodiles and the Australian freshwater crocodile. Once prey is detected, the sawfish sweeps its rostrum sideways to stun its prey. These electroreceptors enable the sawfish to detect the weak electric fields of prey such as as molluscs, crustaceans and slow-moving fishes living on the bottom and in the water column. The top and underside of the saw-like snout or rostrum is covered in thousands of electrosensory ampullae of Lorenzini and several major branches of the motion sensory lateral line. Yellowish to greyish, brown or olive above, white on the underside outer fin margins yellowish brown. To a maximum total length (TL) of 700 cm, usually to 250 cm TL. Two tall, pointed dorsal fins, first originating well forward of pelvic fin origin pelvic fin origin closer to level of first dorsal fin insertion than to its origin pectoral fins distinctly detached from head with broad bases, broadly triangular caudal fin with distinct lower lobe, posterior margin of caudal fin concave. Covered by small tooth-like dermal denticles. Juveniles occur in freshwaters, and upon maturation individuals may move out of rivers, or alternatively attain maturity outside rivers.īody elongate shark-like snout highly modified into a flattened blade-like structure with 18-23 pairs of enlarged lateral tooth-like denticles (rostral teeth) rostral teeth slender with a groove along their posterior margins teeth start near rostral base and are evenly spaced rostrum broad, not tapering distally five gill slits situated ventrally on the head nostrils broad with large nasal flaps barbels are absent numerous very small, rounded-oval teeth in pavement pattern forming bands along jaws. (2004) suggest that the Freshwater Sawfish is better described as a ‘marine opportunist’, and not as a ‘freshwater’ species. It inhabits inshore coastal waters, estuaries, river mouths lagoons, and large rivers. The Freshwater Sawfish is a euryhaline species, able to move through salinity gradients. In the Fitzroy River system of northern Western Australia, the species has been recorded more than 400 km from the sea. In Australia, the species is known from 80 Mile Beach in Western Australia to Princess Charlotte Bay on the east coast of Queensland, with a single anomalous catch from Cape Naturaliste in southwestern Western Australia in 2007 (Phillips 2012). Historically widespread in marine, estuarine and freshwater waters of the Eastern Atlantic, Western Atlantic, Eastern Pacific and Indo-West Pacific - with 4 genetically distinct populations. The Freshwater Sawfish is now extinct or severely depleted in numbers in much of its former range. Pristis pristis (Linnaeus 1758) More Info
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