Lift up a rock and you know there was a fish there, but it vanishes. Lift another in a pool where there is nowhere to hide and a fish darts around and then still manages to vanish into an impossibly small hole. This is the blenny - Lipophyrys pholis. Also known as; Shanny, Sea-frog, Shan, Rockies, Clunny and several other local names that testify this is a very popular little creature.
To make sure it’s a common blenny and not a goby gently lift the dorsal fin (on the back) if it is one continuous fin it is a blenny. The first section is spiny the rear soft, in a goby, it is distinctively two fins. If it has tentacles on the head (over the eyes) it will be a Tompot blenny, a crest between the eyes is a Montagu’s blenny. The Tompot is found at the low spring tide level and the Montagu's is not common.
They have a cryptic camouflage patterning and this differs between ages, sexes and individuals, the males in full breeding condition can be almost black. Breeding takes place in spring in shallow water, they are very common in the rockpools here. Eggs are laid as a mass on a rock and if you find them remember the location, as they mature they become hundreds of little eyes in jelly. The male looks after the eggs and newly hatched young.
As you walk around pools you might hear them plop as they leap into the water, the fish will leave the oxygen-poor water and sit in the open air, I think they like to sunbathe. They have a sort of grumpy face, with large lips and mouth, behind these are some very hard and sharp teeth, I have only been bitten once and it instantly bled. These are used to crush/remove barnacles and topshells, and no doubt nibble on crabs. Blennies have excellent eyesight and they will spot you or pick up vibrations, they are good food for a range of birds so it pays to be alert. Most know the pools in which they live and know exactly where to go if threatened. Once the tide is in they will happily defend their territory including from you. To have a blenny come at you underwater is very funny as they literally come to your mask and try to scare you away. They are also far easier to approach underwater, for some reason they will happily just lay on a rock inches from you.
Blennies are great fun to catch, tie a bit of bacon to a thin string and as they come to eat pull it towards you over your net (don’t use hooks). They are extremely inquisitive fish and rock pooling just wouldn’t be the same without this iconic creature.