The ocean floor is home to some odd beasts. The Japanese sawshark (Pristiophorus japonicus) is definitely one of the strangest. It’s very easy to see where the name comes from: the long, flat snout bears about 25-45 serrated teeth on either side. So with its long slender body, this marine creature is basically a swimming saw.
Right in the middle of the snout, two whisker-like Barbels give the sawshark the appearance of having a long, thin mustache.
This funny-looking fish is an uncommon inhabitant in the waters of Asia’s Northwest Pacific region. It belongs to the sawshark family (Pristiophoridae).
Japanese Sawshark Facts
This sawshark’s long “nose” makes up about 20% of the body’s entire length.
The dorsal and pectoral fins are covered with plates known as placoid scales (aka dermal denticles). These tough scales are actually modified teeth, found only on cartilaginous fish (sharks and rays, also known as elasmobranchs). They have bony, spiny projections – because they grow with their tips pointing backwards – and a hard, enamel-like coating. This gives shark skin a rough feel. The scales provide protection (from predators, external parasites and injury), reduction of drag from friction while swimming, and a place for the skin to hold bioluminescent and sensory organs.
Habitat and Range
The Japanese sawshark lives in temperate areas along continental shelves and coastal waters. Its geographic range in the Northwest Pacific includes the waters off Japan, northern China (East China Sea, Yellow Sea, Bohai Sea,) the Republic of Taiwan, and Korea’s southwest. It does not occur in the Western Central Pacific.
The preferred habitat is sandy or muddy sea bottoms at depths of 50 to 800 m (165 to 2670 ft). The species is thought to make vertical migrations in the water column, according to water temperature, from shallow coastal waters to the upper continental slope.
The Japanese sawshark feeds on small organisms that are buried in the ocean substrate (sand/mud). It uses its sensitive Barbels to poke the bottom with its snout and locate suitable morsels of food. The diet includes fish, squid, shrimp and other crustaceans.
The hunting process is aided by organs called the ampullae of Lorenzini. These electro-receptors are located on the underside of the “saw”. Once the prey is located, the weapon-like snout is used to uncover and then immobilize it.
Adults mature at about 1 m (3.3 ft) in length, and may grow to a maximum of about 1.5 m (5 ft). These sharks are Ovoviviparous, with 12 live pups birthed in each litter. The size of newborn sharks is approximately 30 cm (12″).
Humans and Conservation
This species is harmless to people. It has little importance to fisheries, except in Japan where its meat is considered to be high-quality and it is sought for human consumption. Like many sharks, the sawshark is captured accidentally as “Bycatch” in many fisheries.
The International Union for Conservation of Nature Red List categorizes the Japanese Sawshark as “Data Deficient” because it is uncommon across its range, and so little information is available about its populations.
Written By: Kara Lefevre
Raschi W & Tabit C (1992). Functional aspects of placoid scales: A review and update. Australian Journal of Marine and Freshwater Research 43:123-147.
Wang Y, Tanaka S & Nakaya K (2009). Pristiophorus japonicus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2.