southern bluefin tuna
Thunnus maccoyii · Scombridae · predator
Large southern open-sea tuna, reaching 245 cm, highly prized in Japan. It is endangered worldwide, but is not on the Brazilian national list of threatened species.
Also called: atum-rabilho-do-sul, aleta azul del sur, atún del sur, southern bluefin tuna
- maximum
- 245 cm
- record/max.
- 260.0 kg
- depth
- 0–2,743 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…
—
hour by hour
slide your finger or mouse over the chart to see each hoursee 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 southern bluefin tuna
who is the southern bluefin tuna
The southern bluefin tuna is a tuna of the family Scombridae, very large, reaching 245 cm and up to 260 kg. It lives in open sea, in cold and temperate waters of the Atlantic, Indian and Pacific oceans, mainly between 30° and 50° south latitude, and makes long migrations. It feeds on a wide variety of fish, crustaceans and cephalopods. It has commercial fishing, is farmed in aquaculture, and is highly prized in Japan for sashimi. If fishing continues at the current rate, the population could fall below 500 adults in 100 years.
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 southern bluefin tuna; in the meantime, see the similar species.
fun facts
- During spawning, large individuals migrate to tropical seas, west of Australia.
- It is not known whether the adults spawn every year, at intervals, or only once in their lives.
identification
Very large, fusiform body, highest near the middle of the base of the first dorsal fin. The lower flanks and belly are silvery white, with pale transverse lines alternating with rows of pale dots. The first dorsal is yellow or bluish, the anal and finlets are dark yellow with a black edge, and the keel at the middle of the tail is yellow in adults.
where found
Lives in cold and temperate seas of the Atlantic, Indian and Pacific oceans, mainly between 30° and 50° south latitude, reaching close to 60° south. In Latin America it occurs in Brazil, Argentina and Uruguay.
Habitat: Open sea, in cold and temperate waters, from the surface to great depths.
coast
rules for the southern bluefin tuna
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.
Harmless to handle. Being a large, heavy fish, handle it with support, without forcing the head or the tail. As the species is threatened worldwide, release the specimens you won't keep.
in the kitchen
Much of the catch goes to canning, and tuna of sashimi quality is highly prized, especially in Japan.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.01259, b = 3.03; 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
—
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: Thunnus maccoyii (ficha da espécie)Size, length-weight, depth, habitat, distribution, biology, and IUCN status. Page checked on Oct 13, 2026.
- scientific FishBase: nomes populares de Thunnus maccoyiiNames 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.
similar species
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: