Yarrell’s and snake: the bashful blennies

Yarrell’s blenny – named after an eminent 19th century zoologist, William Yarrell – is a slender-bodied fish easily identified by two fringed tentacles protruding from the top of its head. There are two smaller tentacles between its eyes and the front spines of its dorsal fin are tipped with similar tufted filaments.

It has a single dorsal fin, composed of slender spines. The first two spines have a small flap of skin at the tip that – along with the tentacles – are larger in adult males than in juveniles or females. It is yellow-brown with dark bands across its back and has a conspicuous dark ring around the eye which runs across its cheek.

Yarrell's blenny distribution Yarrell’s blenny is abundant off Norway and Iceland and appears randomly along British and Irish Atlantic coasts. The snake blenny is also a north Atlantic fish, but doesn’t extend to southern England and Ireland

YARRELL’S BLENNY

  • Scientific name: Chirolophis ascanii
  • Maximum weight: 3oz (85g)
  • Average weight: 2oz (57g)
  • Maximum length: 10in (25cm)
  • Life-span: Not known

SNAKE BLENNY

  • Scientific name: Lumpenus lumpretaeformis
  • Maximum weight: 21/2oz (70g)
  • Average weight: 2oz (57g)
  • Maximum length: 20in (50cm)
  • Life-span: Not known

Chirolophis ascanii

Yarrell’s blenny rarely ventures from its rocky home, but this one decided to come out and rub shoulders with a starfish. Chirolophis ascanii The Yarrell’s palm treelike tentacles and distinctive colouring make it one of the most easily recognizable of the eight British blenny species.

The snake blenny has a very long, thin, almost eel-like body. Its back is pale brown, shading to a bluish-grey on its belly with irregular brown blotches on the sides.

Its dorsal fin has a very long base, as does the anal fin, and both are entirely supported by spines instead of rays. The first five spines are very short, as are the last few spines. The tail fin is pointed and the pelvic fin is soft but, unlike the Yarrell’s blenny, it has no head or fin tentacles.

Hide and seek

Both these spiny blennies are secretive fish. Yarrell’s blenny lives in crevices in rock faces, between boulders or in the cavernous hulks of wrecks, often hiding with just its head protruding.

It lives at depths of about 10m (33ft) down to 175m (575ft), but may occasionally be found in shallower water than this.

The snake blenny is mostly found in depths of 40-100m (130-330ft). It burrows into fairly firm muddy bottoms — in which it is difficult to observe – and it often appears in the nets of trawled Dublin Bay prawns. It is possible that the snake blenny shares the prawn’s burrow.

Food of the cods

The Yarrell’s blenny appears to eat small molluscs, worms and brittle stars, and the snake blenny takes the same general food, with the addition of small crustaceans. The snake blenny is occasionally found in the stomachs of such fish as cod and halibut that feed close to muddy bottoms.

Yarrell’s blenny probably lays its eggs in rock crevices and they may be guarded by one of the adults. Newly hatched young have been found among plankton in spring, although in colder, northerly waters, eggs do not hatch until early summer. Less still is known about the breeding of the snake blenny, but it is thought to spawn in midwinter. Their young are also pelagic – floating in the open sea – until they take up life on the sea bed at about three months old.

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