Yellowmouth grouper (Mycteroperca interstitialis)

Side view of a yellowmouth grouper
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Yellowmouth grouper fact file

Yellowmouth grouper description

GenusMycteroperca (1)

The yellowmouth grouper is a fairly large and robust fish which gains its common name from the yellow colouration around the contours of the mouth. The rest of the body is generally a light brownish-grey, paler below, with small, densely packed brown spots on the upper side. The front part of the dorsal fin has a yellow margin, while the rounded pectoral fins are clear, with a white edge and dark coloured fin rays (2) (3) (4) (5). Some individuals are more uniformly brown, while others have faint vertical bars (2) (3). The tail of the yellowmouth grouper has a notched margin. Another distinctive feature is the angular operculum (the bony flap covering the gills), which has a distinct notch and a spiny lobe (2) (3) (4) (5). Although potentially growing to over 70 centimetres, most yellowmouth groupers measure closer to 40 centimetres (4) (5).

In contrast to the adult, the juvenile yellowmouth grouper is quite strikingly bicoloured, being dark brown above, sometimes with broad dark bars or saddle-like blotches, and white below, with a white stripe down the midline of the back from the tip of the lower jaw to the base of the dorsal fin (2) (3) (4). The yellowmouth grouper is very similar in appearance to its close relative Mycteroperca phenax, with both commonly identified as ‘scamp’ (2) (6). The two are only really separated on the basis of slight differences in body and fin proportions, and by the yellowmouth grouper’s lack of dark spots on the dorsal and anal fin (2).

Also known as
blake, crossband rockfish, grey mannock, hamlet, harlequin rockfish, princess rockfish, rockfish, salmon grouper, salmon rock fish, scamp.
Labrus gvaza, Mycteroperca calliura, Mycteroperca dimidiata, Mycteroperca falcata, Mycteroperca roquensis, Serranus dimidiatus, Serranus falcatus, Serranus interstitialis, Trisotropis chlorostomus.
Badeche Gueule Jaune.
Abadejo Salmon, Badejo, Badejo-amarelo, Blake, Cherna Boca Amarilla, Cuna Amarilla, Cuna Chulinga, Cuna Raba Rajao.
Total length: up to 74 cm (2)
up to 7 kg (2)

Yellowmouth grouper biology

The yellowmouth grouper feeds on fish (1) (2) (3) (4) (6), and juveniles show an intriguing behaviour in order to approach otherwise wary prey. Known as ‘aggressive mimics’, the colouration of the juveniles mimics that of the clown wrasse, Halichoeres maculipinna, a species that is harmless to the yellowmouth grouper’s prey. The deception is further enhanced by folding down the fins, adding to the wrasse imitation (1) (7).

Like many groupers, the yellowmouth grouper has an unusual life history, known as protogynous hermaphroditism. All yellowmouth groupers start life as females, reaching maturity at around 40 to 45 centimetres in length, at an age of 2 to 4 years. However, between the ages of around 5 to 14 years old (at a length of 50 to 64 centimetres), individuals change sex and become male (6). Yellowmouth groupers may spawn at any time of year, although peaks have been recorded between April and May in the Gulf of Mexico (6). Juveniles grow rapidly during the first two years of life, after which growth slows significantly. The lifespan of this species may be long, reportedly up to 41 years (6) (8).


Yellowmouth grouper range

The yellowmouth grouper occurs in the western Atlantic Ocean, where it has been recorded from Florida and Bermuda, through the Gulf of Mexico and the Caribbean, and as far south as southern Brazil (1) (2) (3) (4).


Yellowmouth grouper habitat

This species occurs on coral reefs, and is mainly found over rocky or coral bottoms, to depths of up to 150 metres (1) (2) (3) (5). Smaller individuals often occur in mangrove-lined lagoons, and the species is reported to be more common in island waters than along the coast (1).


Yellowmouth grouper status

Classified as Vulnerable (VU) on the IUCN Red List (1).

IUCN Red List species status – Vulnerable


Yellowmouth grouper threats

The yellowmouth grouper is believed to be naturally uncommon throughout its range, and as such is not a major target species in fisheries (1), although it is targeted commercially in some areas (1) (2) (4). The species is often taken along with the similar but more abundant M. phenax, and the two are marketed together as “scamp” (1) (6). Population declines have been noted for this species, which, like many groupers, is particularly vulnerable to overexploitation due to its slow growth, long life span and unusual life history (1) (9). Many of the larger grouper species come together in large numbers at specific locations to spawn, and these spawning aggregations are often targeted by fisheries, posing a further threat to these species (9) (10). However, this may be slightly less of a threat to the yellowmouth grouper, since it spawns throughout the year and so is less likely to form such large aggregations (6).


Yellowmouth grouper conservation

There are not known to be any specific conservation measures currently in place for the yellowmouth grouper, although it may receive some protection from its occurrence in several Marine Protected Areas (1). In unprotected areas, management of harvests is needed (1), and there are also calls for the better protection and management of the spawning aggregations of grouper species (9) (10).

View information on this species at the UNEP World Conservation Monitoring Centre.

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Anal fin
In fish, an unpaired fin on the under surface of a fish, behind the anus.
Dorsal fin
The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
Pectoral fins
In fish, the pair of fins that are found one on each side of the body just behind the gills. They are generally used for balancing and braking.
Protogynous hermaphroditism
A system in which an animal begins its life cycle as a female, but as it ages, based on internal or external triggers, it shifts sex to become a male animal.
The production or depositing of large quantities of eggs in water.


  1. IUCN Red List (June, 2010)
  2. Heemstra, P.C. and Randall, J.E. (1993) FAO Species Catalogue. Volume 16. Groupers of the World (Family Serranidae, Subfamily Epinephelinae). An Annotated and Illustrated Catalogue of the Grouper, Rockcod, Hind, Coral Grouper, and Lyretail Species Known to Date. FAO Fisheries Synopsis No. 125, Vol. 16. Food and Agriculture Organisation of the United Nations, Rome. Available at:
  3. McEachran, J.D. and Fechhelm, J.D. (2005) Fishes of the Gulf of Mexico. Volume 2: Scorpaeniformes to Tetraodontiformes. University of Texas Press, Austin, Texas.
  4. Szpilman, M. (2000) Peixes Marinhos do Brasil: Guia Prático de Identificação. Mauad Editora, Rio de Janeiro, Brazil.
  5. Cervigón, F., Cipriani, R., Fischer, W., Garibaldi, L., Hendrickx, M., Lemus, A.J., Márquez, R., Poutiers, J.M., Robaina, G. and Rodriquez, B. (1992) Fichas FAO de Identificación de Especies para los Fines de la Pesca. Guia de Campo de las Especies Comerciales Marinas y de Aguas Salobres de la Costa Septentrional de Sur America. FAO, Rome.
  6. Bullock, L.H. and Murphy, M.D. (1994) Aspects of the life history of the yellowmouth grouper, Mycteroperca interstitialis, in the eastern Gulf of Mexico. Bulletin of Marine Science, 55(1): 30-45.
  7. Sazima, I. (2002) Juvenile snooks (Centropomidae) as mimics of mojarras (Gerreidae), with a review of aggressive mimicry in fishes. Environmental Biology of Fishes, 65: 37-45.
  8. Manickchand-Heileman, S.C. and Phillip, D.A.T. (2000) Age and growth of the yellowedge grouper, Epinephelus flavolimbatus, and the yellowmouth grouper, Mycteroperca interstitialis, off Trinidad and Tobago. Fishery Bulletin, 98(2): 290-298.
  9. IUCN/SSC Groupers and Wrasses Specialist Group (June, 2010)
  10. Society for the Conservation of Reef Fish Aggregations (June, 2010)

Image credit

Side view of a yellowmouth grouper  
Side view of a yellowmouth grouper

© Florent Charpin

Florent Charpin


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