Angelshark
The angelsharks are a group of sharks in the genus Squatina of the family Squatinidae. They commonly inhabit sandy seabeds close to 150 m (490 ft) in depth. Many species are now classified as critically endangered by the International Union for Conservation of Nature. Once common over large areas of the Northeast Atlantic from Norway, Sweden, Morocco, and the Canary Islands, to the Mediterranean and Black Seas, there is now significant fishing pressure which has resulted in significant population decline.
Squatinidae are unusual in having flattened bodies and broad pectoral fins that give them a strong resemblance to rays. This genus is the only one in its family and order Squatiniformes. They occur worldwide in temperate and tropical seas. Most species inhabit shallow temperate or tropical seas, but a few species inhabit deeper water, down to 1,300 m (4,300 ft).[2] Angel sharks are sometimes called monkfish, although this name is also applied to members of the genus Lophius.
While some species occur over a wide geographic range, the majority are restricted to a smaller area. Restriction in geographic range might be as a result of the behavior of Squatina species, which are ambush predators with a corresponding stationary bottom-dwelling habit. Thus, trans-ocean migration is extremely unlikely, even though large-scale coastal migratory patterns have been reported in species such as Squatina squatina.[3]
The angel shark has unique features that differentiates them from other sharks. They are considered as smaller sized sharks because they grow up to only 7 feet (2.1 m) and can weigh around 77 pounds (35 kg), as opposed to the whale shark that can measure up to 32 feet (9.8 m) and weigh 20,000 pounds (9,100 kg).
While the anterior part of the angel shark's body is broad and flattened, the posterior part retains a muscular appearance more typical of other sharks. The eyes and spiracles are dorsal and the five gill slits are on its back. Both the pectoral and pelvic fins are large and held horizontally. There are two dorsal fins, no anal fin and unusually for sharks, the lower lobe of the caudal fin is longer than the upper lobe. Most types grow to a length of 1.5 m (5 ft), with the Japanese angel shark, known to reach 2 m.[4]Some angel sharks have deformities that have been described in elasmobranchs. These can include skeletal deformities, as lateral spinal curvature (scoliosis), humpback curvature (khyphosis), axial spinal curvature (lordosis), missing fins, additional fins, deformed snout, and more. These abnormalities have only been found in a few sharks, but the causes of these deformities have been found to be from dietary nutritional imbalance, genetic factors, parasites, traumatic injuries, or stress in the specimen. In 2015, two sharks were captured and examined, and both showed a lateral spinal curvature (scoliosis) and also a humpback curvature. Both the animals had the curvature in the middle of their pectoral fins, but the deformity did not affect their swimming capacity.
Spinal scoliosis has been reported to be diverse in sharks, but mostly in pelagic sharks that depend on their swimming abilities to catch their prey. For the angel shark, specifically S. squatina, these curvatures do not seem to significantly affect its hunting capacity, which involves burying itself to ambush their prey. Right now, research is assuming most physical injuries are caused by human interactions because of the constant interference in coastal areas, where most of the sharks reside. There have been few attacks reported, and what few have occurred were due to accidental stepping on of buried newborn sharks.[5] Landings of Pacific angel shark increased through the mid-1980s and reached over 1125 tonnes in 1986, becoming the shark species with the highest total reported landings off the US West coast that year.[6]
