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Andy Horton spends a year examining the biology and behaviour of the rock pool fish and other marine life.



British Marine Life Study Society


Photograph by Andy Horton

Common Name(s):
Smooth Blenny, Common Blenny, Shanny or Shan (Cornwall), Sea-Frog, Rockies, Clunny, Bunners (Dorset)
Mordocet (Caen, France). Cabot's (Jersey, Wales)
Scientific Name: Lipophrys pholis(=Blennius
Usual Size: 165 mm,  Record Weight:  111 g


A small to medium-sized blenny, elongate small fish of a large family of fishes that live in rocky areas in shallow water. All true blennies have a continuous dorsal fin; the first dorsal fins spiny and the remainder soft. The pectoral fins are relatively large. The pelvic fin is in a jugular position. 

Photograph by Andy Horton (1979)

Distinguished by the absence of tentacles/lappets over the eye. Usually green with black mottling, adults may be grey with black. Males in breeding livery go all black with a white mouth and an attractive pale blue fringe to the long dorsal fin. 
If the small green blenny has blue spots and a lappet over the eye it is the similar but rarer Coryphoblennius galerita
Similar species: Coryphoblennius galerita; Parablennius gattorugine (Tompot Blenny). and the Peacock Blenny, Salaria pavo.
The presence or absence of the eye tentacles are definitive. See link.
Paralipophrys trigloides  (southern species:  Fishbase entry)

Blenny from Malta (identified as Paralipophrys trigloides)
Paralipophrys trigloides (link)

Spring, in very shallow water, sometimes intertidal. 
In Sussex, intertidal breeding occurs, but I expect it also occurs offshore, because of the abundance of the young on the shore in summer.
Breeding Congregation (Link to a Photograph)
Breeding Report:
The male in breeding livery goes dark , almost black, with white lips. 

I have a tank in which I have a blenny that has laid eggs. A blenny laid eggs on the side of the tank A month or two ago but despite my attempts I was unable to stop the wrasse in my tank eating them, in fact it was their jaw noise that alerted me to the eggs.
I now have on both sides of rock (an overhang) a patch of eggs that is about 2 inches square completely covered in eggs. It is nearly impossible for the wrasse to get these. I also have two blennies which appear to be laying over the eggs like a bird does over its eggs. Sometimes there is the one, a blenny which appears to have gone very black and a lighter one replaces it every so often . What can I expect , anything? , What can I do to help? Do blennies lay eggs and then one of them has to fertilise the eggs once laid?

   Andy Byres 

With a bit of luck you should have hundreds, possibly thousands of Blenny fry in a week or two. I made a 25% water change prior to the eggs hatching and I was surprised at the numbers of fry because it did not realise they had laid eggs. The water change may have helped the eggs to hatch, or they may have hatched anyway. I don't know. The Blennies bred the following year. I have never been able to get any other Blennies to breed. Getting a pair maybe the reason and Blennies that have been grown to full size in aquaria do not seem to be so keen. The darker male Blenny guards the eggs and the lighter one is the female.

My observations of the Common Blenny of the NE Atlantic, indicate that hatching can be provoked by making a large water change corresponding to physical pressure on the eggs, perhaps corresponding to wave action as this small fish breeds intertidally and in shallow water.

Rocky areas below low water mark,  intertidal (mid-shore and below) from spring to autumn*, under rocks, in crevices and rock pools, especially the juveniles. This fish habitually leaves oxygen-deficient pools and can be seen basking on rocks and completely out of the water at low tide. 

         Photograph by Wayne Curtis (Sunderland)

(* in the south-west this fish can be found on the shore during the winter). 
Gregarious, but there have been reports of serious fighting in aquaria. 

Food: Small invertebrates including acorn barnacles, molluscs especially the Grey Topshell, Gibbula cineraria.
Range:  All British coasts. Not much further afield though. This is a true representative of the British fauna. The prevalence of this fish on north-eastern coasts and north Scotland is not known and any information , including absences, would be of interest. 
It is absent (or very rare) at the Swedish coast, but is present in Norway, a distribution common to many intertidal organisms - there's virtually no tide at the Swedish coast. It is reportedly found in western Norway from Egersund to Sogn. I am fairly sure I saw several
at Bergen.
Michael Norén, Doctoral student.

Southern distribution under enquiry (see Wet Thumb messages.)
Replaced by Paralipophrys trigloides in the Mediterranean.


blennies basking out of the water on rocks above the surface in an aquarium

The Common Blenny is found out of the water at low tide for two reasons:

1)  Left stranded by the receding tide
2)  Jump (hop) habitually out of rock pools deficient in oxygen (or too warm) in hot weather. This happens more often at night. 

Larger fish including Bullheads and Bass
Sea Birds. 

Additional Notes:
A common fish familiar to rockpoolers

I caught a Blenny at Kingston Beach, Shoreham, in early 2013 at a length of 185 mm excluding the tail fin..It was grey in colour. It weighed exactly 2 oz. That is only 56.7 grams though. .

Record Angling Catch:  SHANNY               (Lipophrys pholis)
        3-15   111g      Poldhu Cove, SW. Cornwall      M Carter        1995 

This fish should NOT be collected for live bait because of it lays a small number of eggs would be vulnerable to exploitation, because the large fish on the shore are breeding, with the males guarding the eggs and the females ovigerous. (Males will attack any intruders and bite fingers). Furthermore, collection would spoil to enjoyment of a rocky shore for rockpoolers and other visitors. As a bait it is inferior to live prawn

My daughter (aged 5) caught 6 of these off Lyme Regis Cobb with her crab line using squid bait on July 27 at 16:00 approx.
There were plenty of them and were easily identified - completely spine free and soft.

I found a fish in a rockpool at Lundy Bay near Polzeath in North Cornwall last week (August 2001). I did not know what it was until I identified it on your website.
It was 8 cm long (approx.) and went under the seaweed. 
  Daniel Carlier (aged 10)

Photograph by Andrew Livesey (Dad)

Issac Livesey with a Blenny caught at Brixham, Devon, in July 2002

15 August 2002
The Blenny has grown to 13 cm (excluding its tail fin) in my aquarium. AH
3 October 2003
I wish I kept more accurate notes of capture notes, but it appear that the Blenny, Lipophrys pholis, lives for four or five years in captivity and dies of old age at a length of 155 mm, excluding the tail fin. With the caudal fin the length is 177 mm (7 inches). However, this appears to be the male fish. the females are still living. It could have died for another reason.  AH.
4 February 2004
A Blenny has died in my aquarium at the maximum local length of 15.5 cm (excluding the 22 mm caudal fin). They appear to live 5 or 6 years in captivity. It is the same one or same group as the above.  AH
20 February 2005
My son and I were rockpooling in Bangor on the shores of Belfast Lough, and in the space of two hours we found in the region of forty Common Blennies .  Most of the Blennies were found under large rocks about 10 metres from the low water mark. They ranged in size from approx. 2 cm. to 10 cm. and presumably because they were mating we found up to 11 under one rock.

Report by Tommy Storey.

In medieval times, this fish, known as a Sea Frog, was used as one of the ingredients, with eggs, in hair shampoo, in Italy (related species) and France. (Source: researcher into medieval recipes.)

blenny  | bleni |  n. M18. [f. L blennius f. Gk blennos slime (with ref. to the mucous coating of the scales).] Any of various small spiny-finned marine fishes belonging to the Blenniidae or a related family, most of which are bottom-dwelling fishes of intertidal and shallow inshore waters.
BUTTERFLY blenny. smooth blenny: see SMOOTH a. & adv. viviparous blenny: see VIVIPAROUS 1.

Excerpted from The Oxford Interactive Encyclopedia
Developed by The Learning Company, Inc. Copyright (c) 1997 TLC Properties Inc.

Information wanted: Please send any records of this fish, with location, date, who discovered it, how it was identified, prevalence, common name and any other details to Shorewatch Project EMail Glaucus@hotmail.com. 

Shorewatch Reports

Blennies were especially numerous in May 2000 at Kingston Beach, Shoreham. 

All messages will receive a reply. 
Shorewatch Project
Link: All Species of Blennies from around Britain

Differences between Blennies & Gobies
Information supplied by Andy Horton (British Marine Life Study Society)
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Use these links if your are familiar with the scientific classifications of marine life