The Taiwan angelshark (Squatina formosa) is a shark belonging to the family Squatinidae. They can be found in Taiwan and spotted in the Philippines. They appear yellowish-brown, patterned beautifully in white and brown. The Taiwan angelshark is restricted to a very limited range, and its range is heavily fished commercially. So, although it isn’t a target, the Taiwan angelshark does become a common bycatch unfortunately.
Family: Squatinidae – Angel Sharks
Genus: Squatina
Species: formosa
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– formosa
Status: IUCN Red List ENDANGERED
Average Size and Length: They are born at 33 cm/ 1 foot. Immature females are around 46 cm/ 1.5 feet. Adults are thought to be greater than 100 cm/3.3 feet.
Teeth and Jaw: 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. The teeth are in 3 rows and do not have serrations.
Head: The shape of the head is rounded and around 20 percent of the total body length. The widest part of the head is just before the gill openings, which are on the sides. The barbels are flat, tapering to round tips. There are weakly fringed or smooth anterior nasal flaps. There are no triangular lobes on the lateral head folds. The space between the eyes on the head is concave. The eyes are large. The eye-spiracle space is less than the eye length.
Denticles: There are patches of enlarged dermal denticles on the snout, between the eyes and in rows along the back (when they are young).
Tail: The caudal fin has a lower lobe is larger and more pronounced than the upper lobe.
Demographic, Distribution, Habitat, Environment and Range: The Taiwan angelshark can be found in the northwest Pacific Ocean in Taiwan Island and the Philippines. They can be found on the outer continental shelf and upper slope between 600-1,263 feet.
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 Taiwan angelshark looks much like a skate or a ray, and is yellow-grey or brown with small paired dark ocelli. There are small light spots between the head and the first dorsal fin. There are a lot of small dark brown spots. There are larger irregular blotches. There is a saddle or a band that is along the dorsal fins. The pectoral fins are low, broad and rounded. Both dorsal fins are lobed and are approximately the same size and are spineless. There is no anal fin.
Biology and Reproduction: Their biology and reproduction are poorly known, but more than likely they are ovoviviparous.
Behavioral Traits, Sensing and Intelligence: The Taiwan 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.
Taiwan 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.
Taiwan Angelshark Future and Conservation: The Taiwan angelshark is Endangered by the IUCN, based on suspected population declines of 50-80% within its limited range. While it is not a target of fisheries, it is a frequent and generally retained bycatch of bottom trawling because its restricted range is heavily fished commercially. Like other sharks in its family, the Taiwan angelshark more than likely has a slow reproduction rate and maturity, so it is important to closely watch the stability of this population.
Taiwan Angelshark Recorded Attacks on Humans: Taiwan 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.