Hyporthodus nigritus · Epinephelidae · predator
Giant deep-water grouper reaching 230 cm and 198 kg. Endangered in Brazil, where catching it is banned; in Mexico, grouper fishing closes from February to March.
Also called: mero-negro, Warsaw grouper
Choose the place and the species. The index, from 0 to 100, combines weather, sun, moon and tide with each fish's habits. Up to 28 days, with each day's confidence.
Reading the weather across 3 global models and 31 simulations…
Each card shows the day's index (0 to 100) and, below it, a strip with the index for each hour, from 0h to 23h. from poor to excellent.
Choose how many fishing days. We compare each stretch by its average index, discount days with a warning or closed season, and show the 3 best.
Line: the middle value of 31 simulations of the American GEFS model. Band: where 8 out of 10 fall. Narrow, firm trend; wide, high uncertainty.
The mero-negro (Warsaw grouper) lives in the western Atlantic, from Massachusetts to the Gulf of Mexico and the Caribbean, and reaches Rio de Janeiro and São Paulo. It sits on rocky bottoms from 55 to 525 m, and juveniles sometimes appear on jetties and shallow reefs. It is solitary and eats crabs, shrimp, lobsters and fish. It reaches 230 cm and 198 kg and can live more than 90 years (91 is the longest recorded age). FishBase considers it rare in the Antilles (Cuba, Haiti and Trinidad). The IUCN lists it as Near Threatened, but in Brazil it is on the national list as Endangered and catching it is banned. In Mexico, where it is called mero negro (or fiat), it appears in the NOM for groupers of the Gulf and Caribbean.
Robust body, dark reddish-brown or greyish-brown to nearly black on the back, and dull reddish-grey below. Large head, with a clearly convex forehead and the mouth (maxilla) reaching well past the eye. It has only 10 dorsal spines, one fewer than most groupers, and the rear edge of the preopercle is angular and rounded, with 1 or 2 small spines on the lower edge. The mero (goliath grouper, Epinephelus itajara), also giant, is mottled dark and has small eyes. The yellowedge grouper has yellow fin edges.
In Brazil, FishBase cites Rio de Janeiro and São Paulo, on rocky bottoms of the outer shelf and slope. Outside Brazil, it ranges from Massachusetts to the Gulf of Mexico and the Caribbean, where it is rare in Cuba, Haiti and Trinidad.
Habitat: Rocky bottoms from 55 to 525 m; juveniles sometimes on jetties and shallow reefs.
coast
states
Rio de Janeiro, São Paulo
Living deep, it hardly feels the seasons. It may not be fished in Brazil, and in Mexico grouper fishing closes from February to March.
Any time. On bottoms of 55 to 525 m daylight matters little; current and sea state matter more.
It lives in deep, cold, stable water; a cold front only bothers it through rough seas.
A cold front brings choppy seas and makes it hard to hold station over the spot.
Small effect.
No effect at depth.
Not applicable at sea.
Not very sensitive to noise at that depth.
Strong wind and fast drift keep the bait from staying on the bottom.
Strong current drags the line; with moderate current the fish stays near the bottom.
Adults from 55 to 525 m.
accessories
If a very heavy, dark fish comes up from the rocky bottom, it may be a mero-negro: do not bring it onto the deck, use a descender and return it to the bottom.
Summary of the regulations we found, with the source for each. Rules change; before keeping or transporting fish, check with the state environmental agency.
Conservation: On the national list of threatened species as EN. Global IUCN assessment: NT.
The national list (Portaria GM/MMA nº 1.667/2026) classifies the species as EN. Under Portaria GM/MMA nº 1.666/2026 (art. 3), species listed as VU, EN and CR have full protection: capture, transport, storage, processing and sale are banned. If you hook one by accident, release it right away, with minimal handling.
Source: Portaria GM/MMA nº 1.666/2026, art. 3º, and Portaria GM/MMA nº 1.667/2026
In Mexico, catching all grouper species, a group in which NOM-065 includes the mero-negro (mero negro or fiat), is banned from February 1 to March 31 in federal waters of the Gulf of Mexico off Tabasco, Campeche, Yucatán and Quintana Roo, up to the border with Belize. During the period, bottom longlines are also banned. The agreement does not mention recreational fishing: check with Conapesca whether it applies to your type of fishing.
In federal waters of the Gulf of Mexico and the Caribbean, NOM-065 allows, for domestic-consumption fishing, at most 3 kg per angler per day of any grouper or associated species, such as the mero-negro. The fish is for the angler's and family's consumption only, cannot be sold, and only equipment that one person can operate alone is allowed. Recreational fishing has its own rule (NOM-017-PESC-1994), which we did not check.
Source: NOM-065-SAG/PESC-2014 (DOF Jul 3, 2015), items 4.1 and 4.13 (Sagarpa/Conapesca)
In federal waters around Puerto Rico, beyond 9 miles from the coast, the recreational angler may keep a maximum of 5 fish per day from groupers, snappers and parrotfish combined (up to 15 per boat when there are 3 or more people aboard). The limit does not apply to anyone with a commercial license from Puerto Rico or the U.S. Virgin Islands.
Catch prohibited in Brazil: always release it right away. A fish this large and from deep water suffers greatly out of the water: keep the body horizontal and supported, do not lift it by the mouth alone, and if it arrives with barotrauma (stomach everted, eyes bulging), use a descender.
FishBase says it is sold fresh. In Brazil, catching, transporting and selling it are banned.
Length-weight relationship W = a·Lb (a = 0.01288, b = 3.05; FishBase (relação peso-comprimento bayesiana, estimativa da própria espécie)). It's an average: a fat or lean fish can vary by 10% to 20%.
estimated weight
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The season weights (months), the time of day and the sensitivities (cold, pressure, moon, wind, rain, tide, strong light, murky water and noise) are the app's editorial estimates, based on the literature below and on field experience from anglers and guides. They are not official data or measurements made for this species and may vary by region and year. Closed seasons and legal rules appear in the rules section, with the rule and link. The common size and weight ranges, water temperature and typical depth are also editorial estimates, anchored in FishBase data.
The weather comes from three independent global models, cross-checked hour by hour: when they agree, confidence goes up; when they diverge, the band between them shows on the chart. Beyond 16 days, we use the GEFS ensemble of 31 simulations: if 20 of the 31 predict rain, the chance of rain is 65%. Sun and moon are calculated astronomically, with no uncertainty.
The index adds up, weighted for each species: time of day (species curve anchored to real sunrise and sunset), moon (transits, rise and set, phase), pressure (3 h trend and 24 h swing), water temperature (in rivers, estimated from air temperature; at sea, estimated by an ocean model), wind, rain, clouds, tide and the month in the species' cycle.
Accuracy measured in the reference project (4 regions, 93 days, forecast vs. observed): maximum temperature is off by 0.6 °C on average the next day and 1.7 °C at 7 days; rain of 5 mm or more is detected 76% of the time the next day and 57% at 7 days. Detection isn't everything: the false alarm rate isn't published here yet, and 93 days in 4 regions is still a small sample. We now also measure every day, at the app's destinations:
Your location is saved only on this device and feeds the forecast, the map and the "today" on the home page.
