Carcharhinus obscurus · Carcharhinidae · predator
Large grey-bronze shark, coastal and migratory, with a broad snout and a ridge between the dorsal fins, which lives for decades and is slow to reproduce. Endangered (EN) in Brazil and worldwide: capture banned.
Also called: tubarão-fidalgo, cação-fidalgo
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 dusky shark (tubarão-fidalgo) is a large shark of coastal and shelf waters, not oceanic, which makes long seasonal migrations and appears in the warm and temperate waters of almost the whole world. Adults stay deep, between 200 and 400 m; juveniles in shallower waters. It eats bottom and pelagic fish, other sharks, rays, squid, snails and crustaceans, and sometimes carrion and even objects. It lives a long time (up to about 40 years), takes about 16 months to gestate 3 to 14 pups, and matures large, so the stock recovers very slowly. It is Endangered (EN) on the national list and according to the IUCN. Large adults are potentially dangerous. Do not seek out the species.
Large, robust shark, lead grey or blue-grey above and white below, with a broad, rounded snout, triangular serrated upper teeth and a skin ridge between the two dorsal fins. Pectoral fins of moderate size and curved. In juveniles the fin tips are dark; in adults, plain. It closely resembles the Galapagos shark, from which it is hard to tell apart, and the barriga-d'água, whose first dorsal fin is much taller and more upright. If the shark has a ridge between the dorsal fins and you are unsure, release it.
Western Atlantic from the USA to southern Brazil and Uruguay (FishBase), as well as the eastern Atlantic, Indo-Pacific and eastern Pacific (45°N to 46°S). In Brazil, FishBase cites the south of the country, but the species may appear along the whole coast. On FishBase's Latin American country list: from Mexico and the Caribbean to Ecuador, Venezuela, the Guianas, Brazil and Uruguay.
Habitat: Coastal and shelf waters, from the surface to 400 m; adults usually between 200 and 400 m, juveniles in shallower waters.
coast
Estimate: FishBase cites long seasonal migrations, but with no local calendar; the weights are neutral. Catch is banned year-round.
Any time. There is no reliable data on the activity schedule in Brazil.
Migrates with the seasons; the temperature range varies by region.
Little known effect.
No known effect.
Not very relevant.
Not applicable at sea.
Not well known.
Rough seas make any trip hard.
Little known; juveniles use shallow, coastal waters.
Adults 200 to 400 m; juveniles shallower.
accessories
If a dusky shark bites by accident, release it beside the boat, in the water, cutting the line flush with the hook. Large adults call for care: keep hands and legs away from the mouth.
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 (already on the previous list). Global: Endangered (EN, assessed 06/11/2018 by the IUCN). The whole family Carcharhinidae has been in Appendix II of CITES since 25/11/2023.
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 Brazil, finning is banned: cutting off the fins and discarding the rest of the body. The rule covers landing, transport, and trade by fishing vessels: every shark or ray must arrive whole, with its fins naturally attached to the body (partially folding them against the body is allowed); carrying an animal aboard without fins or with loose fins, and transferring sharks and rays between vessels, is prohibited. This does not authorize catching this species, which is banned.
In recreational sport fishing in Mexican saltwaters, the limit for sharks is one specimen per angler per day, which counts as five toward the total limit of ten fish. Fish caught in sport fishing may not be sold. Catch and release does not count toward the limit: prefer releasing.
In 2021 Colombia stopped considering sharks and marine rays a fishery resource and began treating them as a hydrobiological resource; the recitals of Decree 281/2021 state that they may not be extracted for commercial or sport purposes, and the decree created an environmental protection plan. Later AUNAP rules dealt with incidental catch in artisanal fishing; we did not check the consolidated text. When in doubt, release it into the water.
Law 9 of 2006 bans finning in Panama's jurisdictional waters. The law's definition of shark fishing covers directed or incidental catch by artisanal, commercial, industrial and sport vessels. The fine for artisanal fishing reaches 1,000 balboas, without prejudice to criminal liability. In the sources we checked, we did not find a specific Panamanian rule on retention or release for sport anglers.
This is not catch and release: it is release of accidental catch. Keep the shark in the water, beside the boat, and cut the line as close to the hook as possible. Do not lift it by the tail or take photos out of the water.
Capture and trade banned in Brazil. In other countries the meat, leather, fins and liver oil are used (FishBase), but the species is Endangered: release it.
Length-weight relationship W = a·Lb (a = 0.00794, b = 3.07; 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 seasonal 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. The water temperature range and the common size range are also editorial estimates, supported by FishBase. The months show when an angler usually finds the species, not a catch season. They are not official data or measurements made for this species, and they may vary by region and year. Legal rules appear in the rules section, with the norm and a link.
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.
