The Japanese angelshark (Squatina japonica) is a species of shark belonging to the family Squatinidae. They are found in the northwestern Pacific Ocean off China, Japan, and Korea. They are nocturnal ambush predators. They form a clade with other Asian angelshark species.
Family: Squatinidae – Angel Sharks
Genus: Squatina
Species: japonica
Phylum– Chordata
Class– Chondrichthyles
Subclass– Elasmobranchii
Infraclass– Euselachii
Superorder– Selachimorpha
Common Name– Angel Sharks or Angelsharks
Family– Squatinidae
Common Name– Angel Sharks or Angelsharks
Genus– Squatina
Species– japonica
Status: IUCN Red List VULNERABLE
Average Size and Length: They reach up to 6.6 feet.
Current Rare Mythical Sightings: The Japanese angelshark was described by Dutch ichthyologist Pieter Bleeker in an 1858 volume of the scientific journal Acta Societatis Scientiarum Indo-Neerlandicae. The holotype is a male 53 cm/ 21 inches long, collected off Nagasaki, Japan.
Teeth and Jaw: The wide mouth is terminally placed and has furrows at the corners. They have expendable necks and trap-like jaws that can rapidly snap upwards and hinge shut. They have long, but small, needle-like teeth in the upper and in the lower jaws used for gripping.
Head: Each nostril is large and preceded by a small flap of skin bearing two barbels; the outer barbel is thin, while the inner barbel is cylindrical, and has a spoon-like tip and a smooth to slightly fringed nasal flaps. There are lateral head folds without triangular lobes. The area on the head between the eyes is concave. The eyes are oval and widely spaced. Behind the eyes are crescent-shaped spiracles with large, boxy projections inside their anterior rims. There are five pairs of gill slits located on the sides of the head.
Denticles: There are small thorns on the snout, between the eyes and spiracles and in a row along the back. The denticles are rough, making the skin feel rough.
Tail: The caudal peduncle is flattened with a keel running along either side, and supports a roughly triangular caudal fin with rounded corners. The lower lobe of the caudal fin is larger than the upper.
Demographic, Distribution, Habitat, Environment and Range: The Japanese angelshark can be found in the northwest Pacific Ocean. Hey have been spotted off China, Japan, and Korea. They range from the eastern coast of Honshu, Japan, to Taiwan, and includes the southern Sea of Japan, the Yellow Sea, the East China Sea, and the Taiwan Strait. They prefer cooler temperatures. It is found over the continental shelf, bottom-dwelling, found mostly on the sandy or muddy bottom. More than likely, they reach depths of 980 feet.
Diet: More than likely they feed on fish, crustaceans and cephalopods.
Ram-Suction Index: They have an RSI more towards the suction end of the scale. They lay flat and still on the bottom, when the time comes, they lung at prey and suck it into their mouths with negative pressure.
Aesthetic Identification: The Japanese angelshark has a narrow, flattened shape with pectoral and pelvic fins that give it a wing-like appearance. It is rusty or blackish brown in color. They have small, dense, dark and irregular white spots on the dorsal surface. There are large, paired dark red-brown spots from the base of the head to the pelvic fins. There are no ocelli on the back. It is white ventrally with darker margins on the fins and tail. Its two dorsal fins are placed behind the pelvic fins. The pectoral fins are high, round and broad. The frontmost portion of each pectoral fin forms a triangular lobe separate from the head. The outer corners of the pectoral fins are angular, and their rear tips are rounded. The pelvic fins have convex margins.
Biology and Reproduction: They are presumably ovoviviparous, more than likely giving birth to up to 10 pups per litter. Newborns are thought to be born at 8.7 inches long. Research suggests that females mature sexually at 2.6 feet long, while male maturation size is completely unknown currently.
Parasites include the tapeworms Phyliobothrium marginatum and Tylocephalum squatinae, the copepods Eudactylina squatini and Trebius shiinoi, and the praniza larvae of the isopod Gnathia trimaculata.
Using mitochondrial DNA, a 2010 phylogenetic analysis reported that the Japanese angelshark forms a clade with the other Asian angelsharks included in the study: the Ocellated angelshark (S. tergocellatoides) and the sister species pair of the Taiwan angelshark (S. formosa) and the Indonesian angelshark (S. legnota). These Asian species are, in turn, allied with European and North African angel shark species. Molecular clock estimation suggested the Japanese angelshark lineage diverged from the rest of the Asian angelsharks some 100 million years ago during the Cretaceous period. (Stelbrink, B.; von Rintelen, T.; Cliff, G.; Kriwet, J. (2010). “Molecular systematics and global phylogeography of angel sharks (genus Squatina)”. Molecular Phylogenetics and Evolution. 54 (2): 395–404.
Behavioral Traits, Sensing and Intelligence: The Japanese angelshark lies semi-buried in the sand or on the muddy bottom waiting and ready to ambush prey. They can remain still on the bottom for extremely long and extended periods of time. Research suggest their behavior changes at night, and they are nocturnally active.
Japanese angelsharks have a unique way of breathing compared to most other benthic sharks and fish. They do not pump out water from the oropharyngeal cavity. Instead, they use gill flaps located on the sides of their body to pump out water during respiration. Doing so also allows them to be more unnoticeable and prevent detection from unwanted predators.
Shark Future and Conservation: They are vulnerable due to their limited range and probably slow reproduction. They are valued and taken by trawling fisheries. It is fished in large numbers and used for meat and shagreen, a type of leather. Trawling activity in the Yellow Sea and other parts of the northwestern Pacific is intense and, coupled with pollution, has had a serious impact on the local ecosystem. The Japanese angelshark population is suspected to have declined by up to 50% or more.
Shark Recorded Attacks on Humans: Japanese angelsharks aren’t dangerous to humans unless provoked. Because of their powerful jaws and sharp teeth, they can inflict injury on anyone or anything that may pose a threat to them. There have been cases of Angel sharks biting divers that have tried to restrain them, approach too close to the head, corner them, or grab their tails.