- Scientific name: Chlamydoselachus anguineus
- Also know as: Lizard Shark, Frill-Gilled Shark, Silk Shark, Scaffold Shark
- Size: Up to 6ft in length and 200lbs
- UK minimum size: N/a
- UK shore caught record: N/a
- IUCN status: NT (Near Threatened)
- Distribution: Only British Isles populations are though to be in the very deep waters of the Faroe-Shetland Channel off the north coast of Scotland and the Rockall Trough to the west of Ireland. Also found in isolated and sporadic populations in very deep water locations throughout temperate oceans across the rest of the world.
- Feeds on: Little is known of the feeding habits of the frilled shark. It is thought to feed primarily on squid (which its teeth appear adapted to catch). May also hunt other fish.
- Description: Long eel-like body. Snout and jaws are long and mouth is full of strange multi-pointed teeth. Six gills which continue all around the body and almost meet at the underside. Gills are also filled with frilly gill filaments which give this species its name. Dorsal and anal fins are located very far back on the body. Pectoral fins are relatively large. Lateral line is white and curves upwards above the gills. Eyes are located on the sides of the head. Skin is very rough and the colour is grey to brown.
One of the world’s strangest sea creatures, the frilled shark is a mysterious deep-sea species of shark and very little is known about its life cycle or feeding habits. Despite its eel-like appearance and terminal mouth this species is marked out as a shark by its cartilaginous skeleton, six gills and unsegmented fins. Due to the fact that the frilled shark is a descendant of a lineage of shark species which can be traced back to the Cretaceous period (around ninety-nine million years ago) the frilled shark is often referred to as a ‘living fossil.’ Because of the great depths at which this species lives, and its widely dispersed distribution, few humans will ever set eyes upon a frilled shark, and any that are found are of great interest to the scientific community.
Frilled shark appear to have a worldwide distribution but populations are extremely diffuse (see map), with no concentrated populations appearing to be present anywhere. The most common observations of the frilled shark around the UK come from the very deepest waters with the Faroe-Shetland Channel to the north of Scotland, and the Rockall Trough west of Ireland providing the only frilled shark populations around the British Isles. As the map above shows they are also present throughout European waters from Norway to the coasts of Spain and Portugal and along the western coast of Africa. They are also found in isolated locations in waters off North America, South America, Australia and New Zealand and parts of Asia, especially Japan.
Life Cycle and Feeding Habits
Little is known about the frilled shark and the fact that it is usually found at depths of over one thousand metres makes it difficult to observe or research. It is thought that the cold, deep-water environment means that the frilled shark feeds infrequently and has a very slow metabolism. Although the stomachs of captured frilled sharks have almost always been empty offering scientists little to go on when it comes to working out what frilled sharks eat. It is theorised that squid make up the majority of the frilled shark’s diet, with other smaller fish also being eaten.
It is believed that the multi-pointed teeth of this species are adapted to catching squid. The frilled shark appears to be a fairly slow and cumbersome swimmer, meaning it cannot hunt particularly well. It is thought that the frilled shark may coil up like a snake and strike out quickly over a short distance to catch its prey, while others put forward the theory that the frilled shark can close its gills and suck water – and therefore smaller fish and squid – into its mouth. Another, as yet unproved theory, is that the frilled shark stays still with its mouth open and squid which come to investigate end up getting their tentacles stuck on the points of teeth, and therefore become an easy meal for the frilled shark.
Reproduction and Human Interactions
Frilled shark do not appear to have a specific breeding season and will spawn at any time of the year. The eggs hatch inside of the female and the young continue to grow internally for three to four years until they are around two feet long, when the female will eventually give birth to them. This is one of the longest gestation periods in the animal kingdom. The average litter is six pups. Although frilled shark are not specifically targeted by commercial fishing vessels they are caught in deep-sea trawler’s nets as bycatch. They are either retained to turn into fish meal or thrown back into the sea dead as discard. Long-lines and deep-water gill nets also account for inadvertent catches of frilled sharks, especially around Japan. Due to the slow growth rates of this species, very long gestation periods and the expansion of deep-water commercial fisheries the International Union for the Conservation of Nature (IUCN) class the frilled shark as Near Threatened. The extremely long gestation period and low number of pups means that it is very difficult to repopulate frilled shark numbers if they are reduced. Very occasionally frilled shark can be found in shallow water. It is unknown how they end up so far outside their usual deep water habitat. This footage available on Youtube shows a news report about a frilled shark observed in shallow water off the coast of Japan. This frilled shark was taken to a sea life centre but unfortunately died soon after. This is not usual as deep sea species are adapted to live in the pressures of deep water and are already dying once they find themselves in shallow water. In January 2015 a frilled shark caught by an Australian fishing boat made international news.