Butterfly blenny (Blennius ocellaris)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Blenniiformes · Family: Blenniidae · Genus: Blennius.

Accepted name: Blennius ocellaris · Authority: Linnaeus, 1758 · Taxonomic status: accepted · AphiaID: 126761.

Synonyms and superseded combinations recorded for this taxon: Blennius occelaris Linnaeus, 1758.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=126761 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (FishBase)

Measured values published by FishBase for Blennius ocellaris. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 20 cm · Depth range: 10–400 m · Habitat zone: demersal · Body shape: elongated · Vulnerability index: 10 of 100 · Fishery importance: minor commercial · Aquarium trade: never/rarely.

FishBase notes: Adults are found over hard bottoms. Mainly nocturnal, they feed on small invertebrates. Oviparous. Eggs are demersal and adhesive (Ref. 205), and are attached to the substrate via a filamentous, adhesive pad or pedestal (Ref. 94114).

Eggs are laid under mussel-shells or stones and guarded by the male (Ref. 5981). Larvae are planktonic, often found in shallow, coastal waters (Ref. 94114). Spawn in April (Marseille) or July (England) (Ref. 5981).

Source: FishBase species summary (SpecCode 49) — https://www.fishbase.se/summary/Blennius-ocellaris.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

8,408 georeferenced occurrence records for Blennius ocellaris are published through GBIF from 28 countries or marine areas. The map above plots 178 distinct locations from a sample of 3,000 records, omitting 21 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: Spain (4,817); United Kingdom of Great Britain and Northern Ireland (1,379); France (951); Portugal (540); Ireland (277).

The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.

Source: GBIF Occurrence Search (taxonKey 2395359) — https://www.gbif.org/occurrence/search?taxon_key=2395359&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=126761 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Conservation status (IUCN Red List)

The IUCN Red List assesses Blennius ocellaris Linnaeus, 1758 as Least Concern (code LC). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 185126) — https://www.iucnredlist.org/species/185126/0; GBIF IUCN Red List category endpoint (taxonKey 2395359) — https://api.gbif.org/v1/species/2395359/iucnRedListCategory. Accessed 2026-09-25.

Description and natural history (Wikipedia)

The butterfly blenny has a deep body at the front, tapering rather quickly to the caudal peduncle. It can grow as large as 20 cm in length. It has 11 to 12 dorsal spines, 14 to 16 dorsal soft rays, 2 anal spines and 15 to 16 anal soft rays.

It has tentacles on the nasal opening, above the eye and on the nape near the first dorsal fin ray. The lateral line is discontinuous. The front part of the dorsal fin is much higher than the remainder of the fin, and the anal fin is also long, running half the body length.

The pelvic fins are set well forward and are divided in two. This fish is a mottled brownish-grey, with five to seven dark vertical bars. There is a large bluish-black eyespot surrounded by a white ring on the 6th and 7th rays of the dorsal fin.

The butterfly blenny has a range that extends from the Mediterranean Sea, up the coast of Spain, Portugal and France to the English Channel and the Irish Sea. It is found over rocky substrates covered with seaweed and this means that it is seldom caught in trawls, and may be more common than it seems. It occurs in the subtidal zone, and its depth range is down to about 100 m.

It spawns in late spring (as late as June in the English Channel) and hides the eggs under an abandoned shell; the male guards the eggs. An individual near Plymouth was found to be nesting inside the cavity of a large thigh bone.

Source: Wikipedia: Butterfly blenny — https://en.wikipedia.org/wiki/Butterfly_blenny (CC BY-SA 4.0). Accessed 2026-09-25.