With its bizarre body shape, menacing looks and unusual life-style, the angler fish is unmistakable. It’s one of the ugliest fish in the sea – and not one you’ll see since it spends most of its time hidden on the sea bed, lying in wait for prey to pass by.
Like such sea bed dwellers as skates and rays, the angler has a wide, flattened body that tapers gradually to the tail. Its semicircular mouth is enormous, stretching from one side of its head to the other, and is equipped with long, unevenly spaced, backward-pointing teeth that prevent prey from escaping its clutches.
Camouflage is the key to the angler’s lifestyle – it can change the colour of its skin to match the natural background of any hiding place. Waving fronds of skin break up the fish’s large outline and help to conceal it even further. The underside of its body is pure white, except for the tips of the pelvic fins which are black.
A series of long, separate rays down the head and back is all that remains of the angler’s first dorsal fin. The first – and longest – ray is topped by a leafy flap of skin, at the base of which is a worm-like feature. This ‘rod and lure’ set-up is used by the angler fish to tempt prey towards its mouth. The large pectoral and tail fins help the angler propel its body through the water on the rare occasions when it ventures out for a swim.
Highly adaptable, the angler can live on most types of sea bed. Sand and gravel are its typical habitat, but it is sometimes found on the edge of reefs or rocks where sand patches offer a chance to hide. It is occasionally captured in muddy estuaries.
The most remarkable aspect of the angler’s life is its technique of fishing for food with its ‘rod and lure’. As a potential victim approaches, the angler raises its first dorsal ray above its back and bends it forwards, sometimes jerking the fleshy tip up and down to entice prey closer. The obvious parallel with this technique and that of an angler fishing is how this extraordinary fish came by its name. It is also called the fishing frog.
The prey does not even have to be all that close: when the angler opens its cavernous mouth and throat, the rapid in-rush of water so created carries the victim straight inside.
It feeds on almost any type of fish and bottom-living animal; there are even a few reports of it attacking sea birds sitting on the surface!
Spawning takes place in late spring/early summer in deep water well offshore. The female sheds her eggs in huge ribbon-like, gelatinous sheets, usually one egg thick. These sheets can be up to 9m (30ft) long and 3m (10ft) wide, but they are soon broken up by the waves and widely distributed by the current.
The newly hatched fish stay near the sea surface, kept afloat by the large surface area of their long fin rays. Once they have reached a length of about 8cm (3in) they take up the bottom-living life-style of their parents.