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Mottled grouper: the grouper that profits from the Suez Canal — and has been working its way into the Adriatic since 2000

Among the groupers of the Mediterranean, it's the one with the underbite and the reddish-brown coat: *Mycteroperca rubra* — in English mottled grouper, in German Roter Zackenbarsch (German Wikipedia, Catalogue of Life), less often Gefleckter Zackenbarsch (Catalogue of Life), in Italian cernia rossa, in French badèche rouge or mérou royal, in Spanish abade or gitano, in Portuguese garoupa-chumbo, in Dutch koninklijke grouper, in Finnish viiruposkimeriahven, in Russian пятнистый групер, in Turkish taş hanisi, in Greek πίγκα, in Croatian češljasta kirnja and in Catalan anfós jueu (GBIF, WoRMS, Wikipedia). For Danish, Swedish, Norwegian, Slovenian, Albanian and Japanese we found no confirmed species name in GBIF and Wikidata; for Arabic only the title of the Egyptian Arabic Wikipedia, الهامور مرقش. Here's how to recognise it, where it lives, what it eats, why it gathers in the hundreds to spawn — and why the sources disagree on its size by more than half a metre.

A grouper from “Japan”

It was described by the German naturalist Marcus Élieser Bloch in 1793, at the time as *Epinephelus ruber* (FishBase, English and German Wikipedia). Bloch gave the type locality as “Japan” — according to English Wikipedia probably a mistake for Europe or the Mediterranean. German Wikipedia lists eight further old names, including *Serranus nebulosus* and *Mycteroperca scirenga*. According to Italian Wikipedia, what mainly sets it apart from the groupers of the genus *Epinephelus* is the anal fin: 11–12 soft rays instead of 8–9. According to FishBase it is harmless to humans.

How to recognise it

  • The shape: elongated, robust and laterally compressed; the head is longer than the body is deep (English and German Wikipedia). The lower jaw clearly protrudes, giving the head a pointed shape (Italian, Catalan and Swedish Wikipedia).
  • The colour: usually uniformly reddish-brown, often marbled with black or pale grey blotches (English, German and Swedish Wikipedia). Italian Wikipedia describes whitish spots, arranged in order on the head and irregular on the body — in large fish they can fade or disappear entirely.
  • The line above the mouth: a black streak above the upper jaw (English, German and Swedish Wikipedia).
  • The juvenile mark: a black saddle blotch on the caudal peduncle (English, German and Italian Wikipedia).
  • The gill cover: the preopercle is serrated, with enlarged serrations and a rounded lobe below a notch at the angle (English and German Wikipedia).
  • The teeth: at the front canine-like and well developed, according to Italian Wikipedia four above and two below.
  • The fins: dorsal fin with 11 spines and 15–17 soft rays, anal fin with 3 spines and 11–12 soft rays (FishBase, English and German Wikipedia).

Where it lives — and why it's moving north

Its range is the eastern Atlantic from Portugal to southern Angola and the Mediterranean (FishBase); FishBase gives the bounds as 43° N to 16° S. In the Mediterranean it was long considered a species of the south — according to Italian Wikipedia historically only as far as Sicily. Since the 2000s it has been spreading north: into the Ligurian and Tyrrhenian Seas, along the Italian and French coasts and into the Adriatic (Italian Wikipedia); English Wikipedia names Provence as the northern edge. In Croatia, according to Croatian Wikipedia, it was first caught on 9 September 2000, a few nautical miles off Dubrovnik. It is absent from the Black Sea (English Wikipedia).

It lives on the bottom over rock and adjacent sand (FishBase), according to Croatian Wikipedia above all on steep rocky slopes with stronger currents. It readily takes to artificial reefs and wrecks — English Wikipedia names wrecks off Sicily, Italian Wikipedia wrecks and artificial reefs in general. According to German Wikipedia it usually swims 0.1 to 5 metres above the bottom, lives alone or in groups of up to ten fish, is active by day and retreats into caves and holes at night. Italian Wikipedia often observes it hunting in open water, well above the bottom. Juveniles live closer to shore; FishBase and Catalan and Croatian Wikipedia describe them as very common in mangrove lagoons — there are none in the Mediterranean, so this refers to the African part of its range. For the Mediterranean, German Wikipedia writes that fish up to 10 cm stay in rocky shallows under 10 m all year round.

What it eats — and what the Suez Canal has to do with it

FishBase and Catalan and Swedish Wikipedia name molluscs (probably cephalopods) and small fish, Italian Wikipedia also crustaceans, Croatian Wikipedia mainly cephalopods and fish. German Wikipedia gets specific: in the eastern Mediterranean, rabbitfish (*Siganus*) make up about two thirds of identified prey. These fish arrived from the Red Sea through the Suez Canal — and according to German Wikipedia it is plausible that this new, plentiful food source has made the mottled grouper the most common grouper in the eastern Mediterranean, while it is considerably rarer elsewhere in the Mediterranean.

Female first, then male — and gatherings in the hundreds

Like many groupers it is a protogynous hermaphrodite: every fish starts out as a female, and some later become males (English, German and Italian Wikipedia). According to English, Italian and Swedish Wikipedia the change happens at around nine years and roughly 53 cm. To spawn, they form aggregations: English Wikipedia names such spawning aggregations off Israel, Senegal, Turkey and Corsica. Drawing on a study off Israel, German Wikipedia describes gatherings of up to 500 fish on structure-rich rocky ground, one to two weeks apart throughout the season; the fish showed three colour patterns — dark, spotted and pale — whose function is largely unknown.

Catch, value and danger

According to Italian Wikipedia it is caught with bottom trawls, longlines and by spearfishers; in Europe mostly only occasionally as bycatch in fisheries for other groupers. Its flesh is considered very good (Italian and Croatian Wikipedia), FishBase places it in the “high” price category and mentions a minor commercial fishery. German Wikipedia warns that, depending on where it was caught, eating it can occasionally cause ciguatera poisoning — a fish poisoning caused by algal toxins that accumulate in predatory fish. And it names a particular threat: spearfishing during spawning aggregations, especially on the Israeli coast.

Status — and what you can do

On the IUCN Red List it is classed as “Least Concern”, assessed on 22 November 2016 (FishBase, German Wikipedia). According to German Wikipedia there are no precise population figures. But FishBase rates its resilience as very low: a population needs more than 14 years to double, and its vulnerability to fishing is high to very high (67 out of 100). A fish that gathers in the hundreds at the same rocks and only becomes male at nine years old copes badly with pressure on those gatherings — German Wikipedia says so too.

Whether a minimum size, a closed season or a catch ban applies to it is set by national and regional regulations — there is no universally valid figure, and we deliberately don't give one. Croatian Wikipedia writes, for example, that in Croatia the summer closed season for groupers also applies to it, even though it doesn't belong to the genus *Epinephelus*. Check what currently applies locally — especially in marine protected areas. And if you see lots of large groupers in one spot in spring: that is probably a spawning aggregation, best left in peace.

Seven contradictions in the sources

  • How big does it get? FishBase and English, Italian, Catalan, Croatian and Swedish Wikipedia: up to 144 cm and 49.7 kg, commonly 80 cm. German Wikipedia, by contrast, gives a standard length of 59 cm, a total length of up to about 85 cm and, from observations, up to 95 cm — roughly 50 cm less than all the others.
  • When does it mature? English, Catalan and Swedish Wikipedia: at 27–32 cm and 4–5 years. FishBase: at 34 cm (32–36). German Wikipedia, citing a study off Israel: already at two years, but only at 35–36 cm.
  • When does it spawn? Catalan and Swedish Wikipedia: in the Mediterranean in late spring. German Wikipedia (Israel): from February/March to the end of May.
  • What does the tail fin look like? English Wikipedia: truncate in juveniles and subadults, emarginate in adults over 50 cm. German and Swedish Wikipedia: convex in juveniles under 20 cm, then truncate, emarginate from 50 cm. Catalan Wikipedia simply calls it truncate.
  • How shallow does it live? FishBase and Catalan, Italian, Croatian and Swedish Wikipedia: 15–200 m, mostly 15–50 m. English Wikipedia gives 1–30 m for the eastern Mediterranean, German Wikipedia under 40 m there.
  • Is it fished commercially? English Wikipedia: not in the Mediterranean, because it is too rare there, more often off Africa. FishBase: minor commercial fishery, high price. German Wikipedia: some commercial value, often sold as bycatch in Moroccan markets.
  • Which family? FishBase and German Wikipedia place it in the Epinephelidae, English, Italian, Catalan, Croatian, Swedish and Polish Wikipedia in the sea basses (Serranidae). That's not one side's mistake but an open question of classification — the scientific species name stays the same.

Four name traps

  • “Comb grouper” is used twice. WoRMS, ITIS and the IUCN list comb grouper as a second English name for *Mycteroperca rubra* — English Wikipedia uses the same name for the western Atlantic *Mycteroperca acutirostris*. According to English Wikipedia, records from Brazil were in fact that species.
  • The islands are a mistake. Records from Madeira, the Azores, the Canaries and Cape Verde are, according to German and English Wikipedia, based on confusion with the island grouper *Mycteroperca fusca*; FishBase writes that island records are still unconfirmed.
  • “Mero” on its own is a different fish. GBIF also lists mero for this species — but in Spain mero almost always means the dusky grouper (*Epinephelus marginatus*).
  • “Badèche” on its own is used twice. In French it is called badèche rouge — but mérou badèche is also used for the goldblotch grouper (*Epinephelus costae*). If you want to be sure, use *Mycteroperca rubra*.

That leaves the question every article in this series starts with: when. For a fish that hunts over rocky slopes and wrecks by day and retreats to its cave at night, the right day matters more than any rig. Habitat, prey and spawning season are covered above, and they're fixed. What changes every day are the conditions on your water — StrikeAhead calculates that and tells you when the trip is worth it. And because you don't know the edges and rules of an unfamiliar spot from day one, StrikeAhead Pathfinder tells you who to go out with: curated guides and skippers, personally vetted before listing — licence and insurance —, with verified catches instead of promo photos, no paid ranking and no booking fee for you as an angler. The app says when, Pathfinder with whom.