What does an angelshark look like and how big are they?
The angelshark looks as if it’s half way between a shark and a ray and they only grow to about 2.4 metres long. The have large, billowing fins on their sides, and two small dorsal fins perched atop the tail. They look like they’ve been compressed, and it’s advantageous for them to be as flat as possible as they spend most of their time buried in the sand on the sea bottom.
Three species occur in the eastern Atlantic, but only one, Squatina squatina, is still found in UK waters. This species has white undersides, and they are a dark yellowish colour on top. The hide is broken up by sporadic dots of colour, which aid in camouflaging the fish in the sand.
What’s the difference between Angelsharks and monkfish?
The angelshark used to be referred to as “monkfish.” However, this common name also applies to Lophius piscatorius, a flatfish that feeds in a similar way to an angelshark, leading to confusion. The monkfish is a flat-bodied deep-water fish that uses a lure-like protrusion to attract fish near to its mouth. It then ambushes prey by lunge-feeding, in a similar way to angelsharks. The sharks however do not use a lure, and are not a bony fish.
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How do angelsharks hunt?
The angelshark is an ambush predator, lying still on the ocean floor and waiting for prey to swim close enough for the shark to emerge and engulf them. Only their eyes are visible above the sand. This method of waiting for prey is very efficient, as the sharks expend no energy chasing prey, so they can wait for many days at a time for a meal.
The sharks are also capable of hunting prey in a more traditional manner, by swimming in the water column and attacking. Angelsharks usually stick to one area where they bury themselves, but when prey in the area learn where they are hidden the sharks begin to undertake active hunting.
The fish have nasal barbels, and prominent spiracles behind the eyes. All sharks have these pores behind the eyes and below the snout; they are the receptors that allow them to detect electrical fields. The nasal barbels also allow the shark to detect minute vibrations in the sand, helping the sharks detect bottom-dwelling prey like flounders.
However, a study on Pacific angelsharks revealed that they also rely on visual cues very heavily. When presented with rubber fish, which would not be picked up by the shark’s electrical and vibratory senses, the angel shark still struck and attempted to eat the models.
How does the angelshark avoid detection by prey?
A group of scientists last year released a study on the Japanese angleshark that revealed how it managed to stay so still when hiding in the sand – unlike other fish, the angel shark is capable of concealing its breathing and gill motion so as not to look conspicuous below the sand.
The study showed that unlike other bottom-dwelling fish, the angelshark did not take water into its mouth during respiration, and pump it out through the gill slits. Instead, it utilised gill flaps located on the underside of the body as a pump to eject water through the gill slits, concealing breathing activity below the shark.
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Where do angelsharks live?
Once common in the British Isles, the Mediterranean, the Black Sea, and the North East Atlantic, the species is now classified as regionally extinct in many of the areas it once thrived in, and is critically endangered in the UK.
The angelshark is a bottom-dweller in the ocean. Usually, the only part of it you can see are
its two observant eyes poking out of where it is buried in the sand or mud. It is found in water up to 500 metres deep. The sharks swim the most at night, free hunting or searching for new sandy areas to camouflage in.
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How do anglesharks breathe?
They are also capable of pumping water manually over their gills to breathe, meaning that rather than needing to swim constantly in order to respire, they can afford to spend time motionless. This is essential for their watch-and-wait feeding habits, and gives them a better chance of survival when entangled in fishing nets. As such, training on how to handle the sharks taken as bycatch so that they might survive release is greatly beneficial.
What are the threats to anglesharks?
The main threats to angelsharks include commercial and recreational fishing with almost all gear types, and degradation of habitat. Because of the dramatic decrease in angelshark populations already, genetic diversity within populations is becoming a factor.
The angelshark has no commercial value and is not sought for its meat, or even fins or oil as other sharks are. The main threat to the shark is deep water trawling, where they are caught as bycatch. As they dwell on the sea floor, the sharks are easily affected by this fishing method in particular.
Most deep-sea fish taken as bycatch are dead when hauled up in the nets. The angelshark’s natural adaptations make it more likely to survive collection as bycatch as it does not have a swim bladder that can rupture during pressure changes when it is taken out of the water.
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What are the conservation strategies for angelsharks?
The angelshark is protected in the UK up to 6 nautical miles from the coast. This does not protect the sharks from accidental bycatch, but means they cannot be deliberately taken.
In order to collect better data, it’s important to conservationists to improve the reporting of angelsharks as bycatch by commercial fisheries. Related to this, they endeavour to alert fishermen to the shark’s critically endangered status, and teach them to identify them, and how to handle them when releasing to improve chances of survival.
Angelsharks are a protected species in much of its previous range, but in some places these legal protections are not enforced well. For example, in the Mediterranean, despite protections, they are still caught and killed, so conservationists are pushing for more strict enforcement of protections.