The Sawback Angelshark, Squatina aculeata, is one of three species of Angel Shark that inhabits the Mediterranean. Angel Sharks are a part of the Squatinidae family and are known for their flattened bodies that they use to navigate/hunt along the seafloor. They are a rare species of shark that can be difficult to identify.
Distribution/Habitat
Sawback Angelsharks are mainly found throughout the Mediterranean Sea and adjoining bodies of water. They prefer warmer, tropical waters and migrate to deeper Atlantic Coastal waters in colder months. Like other species of Angel Shark, they are bottom dwellers and occupy continental shelf and upper slope sediment habitats where they can burry themselves in sand or mud. They are mainly found at deeper depths of 30-500m (~100-1700ft), but have been recorded at depths of 1,400m or 4,660ft.
Image courtesy of fisheries.noaa.gov
Feeding Habits
This species of shark are ambush predators. They are nocturnal and spend the majority of the day buried in sand/mud waiting for prey to swim past before they strike. Peak hunting hours for them are around sundown and midnight when their prey is more abundant. They have been known to feed on smaller sharks, bony fish, crustaceans, and cephalopods.
Image courtesy of Simon Rogerson
Appearance
Angel Sharks are a group of sharks that can be identified by their batoid (or flattened) shape, similar to that of a skate or ray. In order to distinguish Sawback Angelsharks from other species there are a few things you can look for:
Image courtesy of NOAA fisheries
- They have a row of dorsal spines that run down the middle of their body, on their snout and above their eyes.
- They have fringed nasal barbels that resemble whiskers.
- They have a camouflaged light and dark brown mottled pattern with white spots that they use to hide themselves in oceanic sediments.
- They have 4 rows of small and sharp teeth.
Image courtesy of iucnssg.org
Females of this species grow to a range of 137 to 143cm (about 4 ½ feet) and weigh up to 22-32kg (~48-71lbs) while males grow to be 120 to 122cm (about 4 feet) and weigh up to 12.7-24kg (~28-53lbs). Females grow larger to be able to carry and support their young.
Reproduction/Lifespan:
Sawback Angelsharks mate during the summer months. It is thought that this could be in correlation with their seasonal migration patterns. Research has shown that they have a 12-month gestation period. They are ovoviparous, meaning they have eggs that hatch internally before giving birth to live offspring. Unborn sharks will grow in the females uterine-cloacal chamber where they are protected from external environments and supplied with vital nutrients before they are released into open waters. Litter sizes usually range from between 8 and 12 pups.
The lifespan of Sawback Angelsharks is unknown, with none in captivity, but other species in the same family are known to live up to 35 years in the wild.
Threats:
The main threat Sawback Angelsharks face is trawl fishing done by commercial and artisanal fisheries. These trawling systems primarily operate within depths where these sharks are found, dragging across the ocean floor and catching/killing Sawback Angelsharks, and other vulnerable species. A sharp decrease in population has been shown in correlation with the start of trawling activities in the Mediterranean and northeast Atlantic. Areas where these sharks were found abundantly are now almost desolate.
Image courtesy of transformbottomtrawling.org
Many fishing vessels harvest these sharks illegally, where their catch goes unreported and unregulated.
Human activity and commercial development are other factors that cause disruption and habitat destruction in areas where these sharks live. Particularly the installation of things like underwater turbines, and toxic heavy metals that have been released into the water from agricultural, industrial, and urban waste.
The Sawback Angelshark was added to the IUCN Red List in 2007 due to overexploitation and remains on that list as Critically Endangered.
Image courtesy of IUCN Red List