doctorfish
Acanthurus chirurgus · Acanthuridae · omnivore
Shallow reef fish with a sharp spine on each side of the tail. It shows up now and then on the line and needs careful handling.
Also called: barbeiro, acaraúna, acaraúna-preta, cirujano, doctorfish
- maximum
- 39 cm
- record/max.
- 5.1 kg
- depth
- 2–15 m
the right time
to be on the water
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…
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hour by hour
tap or drag on the chart to read each hour · on a keyboard, arrow keyssee hour-by-hour table
why this index at —?
choose the day
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.
the fishing month at a glance
what's the best window for the crew?
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.
trend for the coming weeks
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.
everything about the doctorfish
who is the doctorfish
Surgeonfish of the family Acanthuridae, up to 39 cm and 5.1 kg. It lives on shallow reefs and rocky areas, usually between 2 and 15 m, in loose aggregations. It is mainly diurnal and scrapes algae off the bottom, swallowing sand with it. Its larvae are planktonic. Juveniles, at Fernando de Noronha, form cleaning stations with other fish and remove skin and parasites from green sea turtles. In fishing, it sometimes shows up on the line and has small commercial use, besides the aquarium trade.
Essential profile. Identification, where it occurs and rules, with data from FishBase and the cited regulations. Season, time of day, technique and bait are added once we have a good source for the doctorfish.
fun facts
- Juveniles form cleaning stations at Fernando de Noronha, where they remove skin and parasites from green sea turtles.
identification
Short, deep gray body with ten narrow, dark gray vertical bands, well spaced on the flanks. The caudal fin is slightly notched. On each side of the caudal peduncle is a sharp spine that can cause painful wounds. Its short, deep body and dark bands help identify it on reefs.
where found
It occurs in the western Atlantic, from the Gulf of Mexico and the Caribbean to São Paulo, and also in the eastern Atlantic, from Senegal to Ascension Island. In Latin America it lives on reefs and rocky areas of Mexico, Cuba, Venezuela, the Guianas and Brazil.
Habitat: Shallow reefs and rocky bottoms, usually 2 to 15 m deep.
coast
when to fish
best time of day
Daytime. It is mainly diurnal.
rules for the doctorfish
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: Not on the Brazilian national list (Ministerial Ordinance GM/MMA No. 1.667/2026).
We found no species-specific rule beyond the region's general rules.
catch and release
catch and release Releasing the fish alive, quickly and with a wet hand. During a closed season it isn't always allowed: what the regulation says applies.
Be careful with the sharp spine on each side of the caudal peduncle, which can cause painful wounds. Hold the fish by the body, away from the tail, when removing the hook.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.02188, b = 2.96; 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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sources and references
Essential profile: size, length-weight, depth, countries and conservation come from FishBase and the cited regulations, and the texts were written from those sources. Season, time of day, sensitivities, technique and baits and lures are not included yet, because we did not find a good source for this species.
- scientific FishBase: Acanthurus chirurgus (ficha da espécie)Size, length-weight, depth, habitat, distribution, biology, and IUCN status. Page checked on Oct 13, 2026.
- scientific FishBase: nomes populares de Acanthurus chirurgusNames by country and language.
- official Portaria GM/MMA nº 1.667, de 27 de abril de 2026: Lista Nacional Oficial de Espécies da Fauna Ameaçadas de Extinção (peixes e invertebrados aquáticos)The species is not on the list. Checked in the DOU of April 28, 2026.
where each number comes from
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.
sources for this lookup
how accurate the forecast is
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: