The Japanese Bullhead shark (Heterodontus japonicus) is a species of Bullhead shark belonging to the family Heterodontidae found in the northwestern Pacific Ocean off the coasts of Japan, Korea, and China. They are beautifully patterned with 12 irregularly shaped, vertical brown bands and stripes. The Japanese bullhead shark is a docile, slow-swimming shark.
Family: Heterodontidae – Bullhead Sharks
Genus: Heterodontus
Species: japonicus
Phylum– Chordata
Class– Chondrichthyles
Subclass– Elasmobranchii
Infraclass– Euselachii
Superorder– Selachimorpha
Common Name– Bullhead Sharks
Family– Heterodontidae
Common Name– Bullhead Sharks
Genus– Heterodontus
Species– japonicus
Status: IUCN Red List LEAST CONCERN
Average Size and Length: They are born around 7.1 inches. Mature males have been measured at around 2.3 feet. The maximum recorded has been 3.9 feet.
Current Rare Mythical Sightings: The Japanese bullhead shark was originally described as Cestracion japonicus by ichthyologists Nicholas Miklouho-Maclay and William John Macleay, in an 1884 volume of Proceedings of the Linnean Society of New South Wales. The type specimen is a female caught off Tokyo. Other common names used for this species include Bull Head, Cat shark, Japanese Horn shark, Cestracion shark.
Teeth and Jaw: The incurrent opening is encircled by a groove while another groove runs from the excurrent opening to the mouth. The small mouth is positioned nearly at the tip of the snout; the front teeth are small with a sharp central cusp flanked by a pair of lateral cusplets, while the back teeth are broad and rounded. There are deep furrows at the corners of the mouth, extending onto both jaws.
Head: It has a short, blunt head. It has a pig-like snout. The eyes lack a nictitating membrane and are followed by tiny spiracles. Shallow supraorbital ridges are present above the eyes, and the space between them is slightly concave. The nostrils are divided into incurrent and excurrent openings by long flaps of skin that reach the mouth.
Denticles: The dermal denticles are large and rough, particularly on the sides of the body.
Tail: The caudal fin is broad with a short lower lobe and a long upper lobe has a strong ventral notch near the tip.
Demographic, Distribution, Habitat, Environment and Range: The Japanese Bullhead shark can be found in the northwest Pacific in Japan, Korea, North China, and the Taiwan Islands. They are found on the bottom between 20-121 feet. They prefer kelp and rocky locations. They are considered benthic.
Diet: They typically feed on invertebrates and small fish.
Ram-Suction Index: They protrude their jaws to capture prey, then grind it with their molar-like teeth.
Aesthetic Identification: The Japanese Bullhead shark has a cylindrical body and is tan to brown in color. They have 12 irregular dark saddles and bands. There are no spots. There is a light bar between the eyes and a dark blotch under each eye which are indistinct in large adults. The newly hatched pups are much brighter in color and have higher dorsal fins. The first dorsal fin is very large and high, and is somewhat falcate and it originates over the bases of the pectoral fins. The second dorsal fin is much smaller, but similar in shape, and originates over the rear tips of the pelvic fins. Both dorsal fins have stout spines on their leading edges. The pectoral fins are large. The pelvic fins are much smaller than the first dorsal fin. The anal fin is placed well in front of the caudal fin.
Biology and Reproduction: The Japanese Bullhead shark is oviparous They lay pairs of eggs among the rocks or in kelp between 8-9 m during 6-12 spawnings. This happens between March and September but between March and April in Japan. The eggs hatch in about a year. Males attain sexual maturity at a length of 2.3 feet.
The egg case is auger shaped, and has two flanges spiraling around it. At first the case is soft and light brown, and over a few days it hardens and darkens in color.
Known parasites of this species include the copepod Dissonus pastinum, and the haemogregarine protozoan Haemogregarina heterodontii.
Behavioral Traits, Sensing and Intelligence: Several females may share a nest, but they do not guard the eggs.
Speed: Their movement is very sluggish and slow swimming and they can be seen “walking” with their mobile paired fins.
Japanese Bullhead Shark Future and Conservation: They are currently of least concern because they are not of any significant value or importance by commercial fisheries. They are kept in aquaria.
Japanese Bullhead Shark Recorded Attacks on Humans: Harmless to humans (unless stressed), the Japanese Bullhead shark can be easily hand-caught by divers. Their spines can impose a painful wound if not careful.