Marine Life - Lesser-Spotted Dogfish (Scyliorhinus canicula)
Ever been on a dive and seen something you didn’t recognise? The Marine Life pages might help you to recognise the wonderful organisms you have explored in the underwater realm. Read on to find information on such aspects as the feeding, breeding and physiology of some of your favourite marine flora and fauna.
The lesser-spotted dogfish is the most common species of shark encountered by divers in the South-West. Up to 80cm in length it can be found on sandy, rocky or muddy seabeds in shallow coastal waters. It has a blunt head with a rounded snout and, like other, larger sharks, the mouth is positioned on the underside of the head, the skeleton is made of cartilage and the gill slits, just in front of the pectoral fins, are uncovered. Unlike the larger sharks, however, the dorsal fins are small and rounded and positioned well back on the body. The skin of the dogfish consists of tooth-like scales and feels quite smooth if stroked from nose to tail but very rough when stroked in the opposite direction. The shape of these scales differs over various parts of the body and those overlying the jaws function as the teeth. The body is a greyish brown in colour with numerous dark spots and a white underside. Dogfish are often seen resting on the seabed in the day. They hunt at night, feeding mainly on crustaceans (crabs and shrimps) and molluscs (especially whelks), and occasionally on small fish and squid. Dogfish rely heavily on their sense of smell to catch prey and can also detect faint electrical fields produced by the muscles of hidden prey.
Unlike most fish, which simply eject eggs and sperm into the water near each other and rely on random mixing, the lesser-spotted dogfish uses internal fertilisation. The male wraps his body around the female and inserts the sperm with specially adapted pelvic fins known as ‘claspers’. After mating in the autumn, the female comes inshore during the winter or spring to lay her eggs, the distinctive brown capsules known as ‘mermaids’ purses’. The female swims repeatedly around a piece of seaweed to attach the curling tendrils of the egg capsule (approximately 7 cm long) firmly to its anchorage. Each capsule contains a single embryo and a miniature dogfish will emerge approximately 9 months later.
Once thrown overboard as discards, dogfish are now commercially important for
meat (rock salmon), fishmeal and oil and are locally endangered due to over
fishing.
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