Butterfly blenny (Blennius ocellaris)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



Blennius ocellaris reaches up to 20 cm in length. It has one long, continuous and relatively tall dorsal fin with 11 spiny rays and about 14 soft rays. The anterior part of the dorsal fin is noticeably higher than the posterior. It is easily recognisable by the bluish-black spot with a white margin on the dorsal fin. It has one long anal fin running half the length of the body to the tail. The pelvic fins are forked in two and positioned beneath the throat. Its body is deepest at the throat and tapers relatively sharply to the tail. It is mottled light brown to grey in colour with 5-7 darker bars on the body.

Recorded distribution in Britain and Ireland

Usually found in the English Channel and Irish Sea, as far north as the Isle of Man but one sighting puts it as far north as the Outer Hebrides.

Global distribution



The butterfly blenny is a benthic subtidal species, usually found on hard bottoms from 10 m depth down to over 100 m.

Depth range


Identifying features

  • Up to 20 cm in length.
  • Anterior part of the long dorsal fin higher than the posterior.
  • 11 dorsal spines and 14 soft dorsal rays elongated beyond the fin membrane.
  • Forked pelvic fin.
  • Bluish-black spot between dorsal spines 6 and 7.

Additional information

No text entered

Listed by

- none -


  1. Froese, R. & Pauly, D., 2007. Fishbase. A global information system on fishes. [On-line] http://www.fishbase.org, 2008-02-18

  2. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  3. Moen, F.E. & Svensen, E., 2004. Marine Fish & Invertebrates of Northern Europe. Southend-on-Sea: Aqua Press.

  4. Whitehead, P.J.P., Bauchot, M.-L., Hureau, J.-C., Nielson, J. & Tortonese, E. 1986. Fishes of the North-eastern Atlantic and the Mediterranean. Vol. I, II & III. Paris: United Nations Educational, Scientific and Cultural Organisation (UNESCO).


  1. Isle of Wight Local Records Centre, 2017. IOW Natural History & Archaeological Society Marine Records. Occurrence dataset: https://doi.org/10.15468/7axhcw accessed via GBIF.org on 2018-09-27.

  2. National Trust, 2017. National Trust Species Records. Occurrence dataset: https://doi.org/10.15468/opc6g1 accessed via GBIF.org on 2018-10-01.

  3. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  4. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-05-18


This review can be cited as:

Barnes, M.K.S. 2008. Blennius ocellaris Butterfly blenny. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 18-05-2024]. Available from: https://www.marlin.ac.uk/species/detail/160

Last Updated: 02/06/2008