Angel Shark
Squatina australis
Angel sharks exhibit both shark and ray characteristics. They have a flattened body with broad, triangular pectoral fins which are not attached to the head as they are in rays. The pelvic fins are similarly flattened and expand out from the body. Another way the angel shark differs from sharks is their caudal (tail) fin which has a longer lower lobe, which may aid quick movement when searching for prey. They have triangular shaped, extremely sharp teeth and located on either side of the mouth are barbells (antennae) which seek out the chemical reactions of their prey along the sea floor. Angel sharks are perfectly camouflaged against their sandy habitat, varying in colouration from white and grey to brown and black with numerous irregular blotches and spots over the body surface. They are a large species growing to a maximum size of 1.5 metres and live to approximately 25 years of age.
Angel sharks are ambush predators, waiting stationary, partly submerged on the seafloor before launching from the sand surface at unsuspecting fish swimming by catching prey in their trap-like jaws. They are not restricted to fish, feeding on a variety of benthic invertebrates such as molluscs and crustaceans, octopus and squid. Angel sharks are a nocturnal species, actively feeding at night. They are able to target individual fish swimming by due to the bioluminescent wake they leave.
Angel sharks have a worldwide distribution, they are generally not found in the Indian Ocean except for one southwestern corner where the species Squatina australis occurs. The angel shark ranges in subtropical water from Sydney, New South Wales to Rottnest Island, Western Australia. The angel shark inhabits inshore shallow waters to depths of 1,300 metresm along reef fringes.
Populations of the angel shark have been declining due to high commercial fishing pressure, after realisation they are a good eating fish, coupled with low fecundity and their long gestation period. As a result they have been listed as ‘vulnerable’ on the global IUCN redlist. The angel shark is an aplacental viviporous (used to be known as ovoviviporous) species, whereby the eggs hatch within the uterus, and the young are not nourished by a placenta, but a yolk sac which is their only food source until their live birth. Females produce 10 young per litter, with each pup approximately 30 centimetres long at birth.
Other common names include: Australian Angel Shark, Australian Angelfish, Australian Angelfish, Monkfish.
Occurrence at the Busselton Jetty:
A cryptic species, the angel shark is not often observed from the underwater observatory, however has been seen in the shallow waters surround the jetty.
Image by: S. Daniels
