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Ever seen a sawshark?

The sawsharks (Pristiophoriformes) are an order of sharks with long snouts, lined with teeth, used to slash and disable their prey, that is found in sandy bottoms, with the help of their electro-receptors (ampullae of Lorenzini) on the underside of the saw and then taken into the small mouth.

The characteristic mouth and saw with barbels of a sawshark

Most sawshark occur in waters from South Africa to Australia and Japan, at depths of 40 metres (130 ft) and below; in 1960 the Bahamas sawshark was discovered in the deeper waters (640 m to 915 m) of the northwestern Caribbean.
Sawsharks are easily confused with sawfish. They are both elasmobranchii, but the sawshark is a shark, the sawfish is a ray. Sawsharks have a pair of long barbels about halfway along the snout, have two dorsal fins, but no anal fins, and can be up to 170 centimetres in length. Sawfishes have a much larger maximum size, lack barbels, have evenly sized rather than alternating sawteeth, and have gill slits on their undersurface rather than on the side of the head.
Sawsharks mainly feed on small fishes, crustaceans, and squid.

The embryo of a longnose sawshark with attached yolk sac (© Mike Parry)

 

 

 

 

 

 

 

Sawsharks are ovoviviparous, the young develop within their mother and feed on the yolk sac, that is totally re-absorbed before the litter of 7 to 17 pups is born.

There are two genera of this fascinating shark family, the Pristiophorus with five gill slits on each body side, and the Pliotrema, that have six, with as the only species Pliotrema warreni (IUCN Red List Status: Near Threatened, population trend unknown).

There are six described and one not yet described Pristiophorus species:

  • Pristiophorus cirratus, the longnose sawshark, found in the waters off Southern Australia and Tasmania, IUCN Red List Status: Least Concern, population trend stable
  • Pristiophorus japonicus, the Japanese sawshark, found in the North West Pacific, IUCN Red List Status: Data Deficient, population trend unknown
  • Pristiophorus nudipinnis, the shortnose sawshark found in the waters off Southern Australia and Tasmania, IUCN Red List Status: Least Concern, population trend stable
  • Pristiophorus nancyae, the African dwarf sawshark (only discovered in 2011 in Mozambique!), IUCN Red List Status: Data Deficient, population trend unknown
  • Pristiophorus schroederi, the Bahamas sawshark, found in the waters around the Bahamas and South Florida, IUCN Red List Status: Data Deficient, population trend unknown
  • Pristiophorus delicatus, the tropical sawshark, found in the waters off East Australia (formerly described as Pristiophorus species B before it was described), IUCN Red List Status: Least Concern, population trend unknown
  • Pristiophorus species C, Philippine sawshark, found in the Philippines off Apo Island and southern Luzon (not yet described species), IUCN Red List Status: Data Deficient, population trend unknown
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Most sawsharks live in deeper waters above sandy ocean floors, and are not often spotted by divers. People cut off the saw of the saw shark and sell them as artifacts and souvenirs. After this, the shark dies. Saw sharks can easily get entangled in nets and killed by nets and lines, and are very vulnerable for bycatch in demersal fisheries and bottom trawl fishers. They are sold as food or discarded.

 

Do you want to know more about sawsharks? Check out

http://www.iucnredlist.org/search
http://www.fishbase.org/Nomenclature/ScientificNameSearchList.php?
Both sites offer descriptions of species, habitat and status.

 

Some information on this subject was derived from the Collins Field Guide SHARKS of the world (Sarah Fowler, Mark Dando, Leonard Compagno).

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