Dogfish scales are formed like teeth. The shape of the scales varies over different parts of the body and those overlying the jaws function as the conventional teeth. On the body the points are directed backwards. If stroked nose to tail, a dogfish feels quite smooth but in the opposite direction, decidedly spiky. Dried dogfish skin has been used as sandpaper.

Dogfish egg capsules are known as mermaids purses and have long tendrils on the corners. The female swims round and round a clump of seaweed as she lays, so that the eggs become well anchored.The young dogfish emerge around 9 months later as fully-formed miniature adults about 10cm long.

Dogfish rely heavily on their sense of smell when hunting and have been observed slavishly following a scent trail - like a bloodhound - even when their prey has turned and swum right back past them. They are also able to detect faint electrical fields produced by the muscles of hidden prey.

Most fish simply eject eggs and sperm into the water near each other and rely on random mixing - the squirt and hope method. Lesser-spotted dogfish, however, use internal fertilisation, a much more intimate approach.The male wraps his body, in the shape of a ring, around the female. He inserts the sperm with specially adapted pelvic fins known as claspers.

Often seen snoozing on the seabed during the day, dogfish feed at night. They are indiscriminate hunters and munch on crabs and whelks as well as eating bottom-living fish like gobies, dabs and gurnards. They will also hunt shoaling fish such as herring and pilchards.

Dogfish are small sharks and have many shark-like features such as low-slung mouths, hydroplane-like pectoral fins and uncovered gill slits. The species most often seen by British divers is the lesser spotted dogfish, Scyliorhinus canicula. It is also known as the rough hound and in fish shops has the more appetising name of rock salmon.