Dwarf Sawfish

​Another Saturday means another #SawfishSaturday! The next sawfish we are showcasing on TFUI is the dwarf sawfish (Pristis clavata), smaller than other sawfish as it only grows to be about 3 metres (10 feet). Remember, although sawfish look awfully similar to sharks, they are actually ‘modified’ rays that use that long rostrum (snout) back and forth to stun fish before eating them. 

​The dwarf sawfish, also known as the Queensland sawfish, can be found in tropical Australian waters from Cairns to Queensland and all the way to Western Australia (the Kimberley coastline). This distribution may be larger and include neighbouring islands/countries. They seem to prefer coastal and estuarine habitats that have sand and mud flats, and can also be found miles up rivers. It has not been documented in freshwater, however. #Finfact: In Queensland (Australia), the dwarf sawfish can also be simply known as “sawfish.” The status of their population is currently unknown and little has been done to protect them. The IUCN has assessed the dwarf sawfish as Endangered (EN) because they are caught in commercial gillnet and trawl fisheries targeting other species. With such a long rostrum, it’s no wonder they caught! While their meat can be eaten (and other parts of their body utilised) there is no indication that Australians eat them. What do dwarf sawfish eat? We’re not 100% sure! But we’re guessing they like to munch on small fishes and crustaceans.
 
Dwarf sawfish are an olive-brown colour which gets darker on the head that gives way to a creamy underbelly. Their fins are usually lighter than their dorsal side. They are viviparous with yolk-sac, and the gestation period is unknown; how many pups are in a litter has not been reported.
 
How can you tell a sawfish apart from other sawfish? Here are a few differences – we will be talking about these species more in depth in the coming months. Dwarf sawfish can be distinguished from the knifetooth sawfish (Anoxypristis cuspidata) by its teeth (which are sharper in shape than the blade-like ones of A. cuspidata), and the lack of a well-developed lower caudal fin lobe; it can be distinguished from the freshwater sawfish (Pristis microdon) by the lack of a lower caudal fin lobe; it can be distinguished from the largetooth sawfish (Pristis perotteti) by its geographic range; it can be distinguished from the smalltooth sawfish (Pristis pectinata) by having fewer rostral teeth per each side (18-23, versus 20-34 per side); it can be distinguished from the green sawfish (Pristis zijsron) by the second dorsal fin being smaller than the first dorsal fin. In addition to the above, the dwarf sawfish is significantly smaller than any other sawfish species… hence the common name.

​#Finfact: Do you remember how to tell a sawfish apart from a sawshark (Pristiophorus spp.)? It lacks barbels and has similar-sized rostral teeth! You can also differ between the two species by gill placement. Check out our blog post about sawsharks here.
 
Do dwarf sawfish have predators? Probably! They may include hammerhead sharks (Sphyrna spp.), bull sharks (Carcharhinus leucas), bronze whaler sharks (Carcharhinus brachyurus), and saltwater crocodiles (Crocodylus porosus). And we can’t forget: a parasite, Neoheterocotyle darwinensis n. sp., lives in the gills of the dwarf sawfish! Other potential parasites can be copepods, nematodes, protozoans, and trematodes. 

did you know about this sawfish before?

glossary

• Caudal fin: The tail fin.
• Commercial fishery: The activity of catching fish and other seafood for profit.
• Crustaceans: Group of animals with a hard exoskeleton, jointed legs and segmented body.
• Dorsal fin: Fin located on the back.
• Dorsal side: The top of an animal.
• Estuary: Where the tide meets the stream (resulting in a mixture of fresh and salt seawater).
• Gestation: The period in which a fetus develops, beginning with fertilization and ends at birth.
• IUCN: International Union for Conservation of Nature.
• Pups: Baby sharks.
• Rostral teeth: Tooth-like projections on the sides of the snout of sawfishes and sawsharks.
• Rostrum: Snout.
• Trawl fisheries: Fisheries that pull a fishing net through the water behind one or more boats.
• Viviparous with yolk-sac: Also known as aplacental viviparous and previously known as ovoviviparous/ovoviviparity; it is the production of eggs that are fertilised and hatch inside the female shark but the embryos lack a placental connection to the oviduct or uterus and so do not feed off the mother.

say hello!

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