A yellowish shark of reefs, mangroves and shallow lagoons, with two nearly equal dorsal fins. Endangered in Brazil: catch prohibited. Atol das Rocas is one of its nursery areas.
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.
location
Sample location: choose yours to see the forecast for where you fish.
period
Reading the weather across 3 global models and 31 simulations…
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index Score from 0 to 100 for the fishing conditions of each hour. It reads weather, sun, moon, tide and the species' habits. It doesn't promise fish: it tells you when the water is on your side. 0–24 poor · 25–44 fair · 45–64 good · 65–84 very good · 85–100 excellent.
today
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confidence —
confidence How much you can trust the weather forecast for the day. It drops with distance and when the models disagree. It is not the chance of catching fish.
models and trend Up to 16 days, three global weather models (the European ECMWF, the American GFS and a high-resolution blend) read hour by hour; when they disagree, the light band on the chart widens. Beyond that it's a trend: 31 runs of the American GEFS model. Confirm when it's 1 week out.
window Consecutive hours with the index near the day's peak and no danger alert. It is the time to have the bait in the water.
hour by hour
tap or drag on the chart to read each hour · on a keyboard, arrow keys
see hour-by-hour table
why this index at —?
next 7 days
choose the day
chart: bar height = day's index · line = variation between models · striped = trend · fainter = less confidence
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.
4-week calendar
the fishing month at a glance
plan a trip
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.
the species
everything about the lemon shark
overview
who is the lemon shark
The lemon shark lives in warm, shallow waters of the western Atlantic and eastern Pacific: reefs, mangroves, lagoons, bays and river mouths. Pups are born in shallow nurseries and spend their first years there, and females usually return to give birth where they were born. In Brazil it is best known in the Northeast and on oceanic islands, with a well-studied nursery at Atol das Rocas; it also occurs at Fernando de Noronha. It eats fish, rays and crustaceans, mostly at dawn and at night. Because it lives in shallow water and grows slowly, it suffers heavily from nets and lines: in Brazil it is Endangered and catch is prohibited. Elsewhere it is sought on fly and with bait on flats and mangroves.
fun facts
Two decades of genetic studies in the Bahamas showed females returning to give birth in the nursery where they were born.
Atol das Rocas, where many pups grow, is an extreme-tide nursery studied by researchers from Brazil and the United States.
Its two dorsal fins of nearly the same size set it apart from almost every other shark.
how to recognize it
identification
Robust body, yellowish brown to olive gray, with a strong yellow tone; pale belly. Short, broad, rounded snout. Its hallmark is two dorsal fins of nearly equal size, both slightly sickle-shaped. No spots or black tips. The bull shark also has a short snout, but it is gray and its second dorsal is much smaller than its first; the nurse shark has barbels and a flattened body.
Most common in the Northeast and on oceanic islands (Atol das Rocas and Fernando de Noronha); rarer records in the Southeast. In the western Atlantic it ranges from the United States to southern Brazil, including the Bahamas and the Caribbean; in the Pacific, from Baja California to Ecuador.
Habitat: Shallow reefs, lagoons, mangroves, bays and river mouths; pups in shallow, protected nursery areas.
coast
North CoastNortheast CoastSoutheast Coastcoastalshelf
states
Amapá, Pará, Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Sergipe, Bahia, Espírito Santo, Rio de Janeiro, São Paulo
calendar and clock
when to fish
best season
time of year
JanFebSeaAprMayJunJulAugSepOctNovDec
Estimate: present year-round on the reefs and islands of the Northeast. Biological information: in Brazil, catch is prohibited year-round.
best time of day
Night and twilight. Hunts mostly at dawn, at dusk and at night; by day it rests in channels and on the bottom.
weather, water and behavior
what affects the lemon shark
sensitivity The little bars show how much each factor affects this species. Five full: it feels it a lot.
cold and cold fronts
A warm-water species; cold water reduces its activity.
atmospheric pressure
Not very relevant.
moon
Large full-moon and new-moon tides change the circulation in the nursery areas.
rain
Not very relevant.
water level
In atolls, pups follow the rise and fall of the tide between pools and channels.
noise
Juveniles flee boats and people in shallow water.
wind
Not very relevant.
tide
Closely tied to the tide in shallow nursery areas.
depth
Almost always shallow; adults can descend to about 90 m.
technique, gear and bait
how to fish
rod
Catch prohibited in Brazil.
spinning / baitcasting reel
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line
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leader
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hook
For any reef fishing, prefer a barbless circle hook: it makes it easy to release what can't be kept.
accessories
cutting pliers
long hook remover
tip from an angler
If a lemon shark is hooked by accident, release it in the water, cutting the line close to the mouth. Fishing is prohibited in the Atol das Rocas Biological Reserve and in the Fernando de Noronha Marine National Park.
what the law says
rules for the lemon shark
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: Catch prohibited throughout Brazil. Global: Vulnerable (IUCN, September 4, 2020). Listed in CITES Appendix II.
Threatened species (EN): catch prohibited in Brazil
catching, transport, holding and trade prohibited
The lemon shark (Negaprion brevirostris) is on the national list as Endangered (EN) (it was already on the previous list, Portaria MMA 148/2022). Ministerial Ordinance GM/MMA 1.666/2026 (art. 3) prohibits catch, transport, storage, possession, processing and trade throughout Brazil. Anyone who hooks one by chance must release it alive immediately (art. 3, § 4). The rule does not authorize targeted fishing, even with release: in Brazil, do not seek this species.
Finning prohibited: shark only whole, with its fins
fins naturally attached to the body
In Brazil, finning is prohibited (cutting off the fins and discarding the body). Every shark or ray landed must arrive with its fins attached to the body; it is prohibited to carry on board an animal without fins or with loose fins, and to transfer sharks between vessels. It applies to any shark that may be kept.
1 specimen per angler per day (counts as 5 against the quota of 10)
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.
commercial or sport extraction not permittedconfirm with the agency
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.
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.
This is not catch and release: it is release of incidental catch. Keep the shark in the water, cut the line close to the mouth and let it go. Don't hold it up for a photo.
in the kitchen
Catch and trade prohibited in Brazil.
calculator
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.00513, b = 3.09; FishBase (estimativa bayesiana para a espécie e a subfamília, comprimento total)). It's an average: a fat or lean fish can vary by 10% to 20%.
estimated weight
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sources and references
The seasonal weights (months), time of day and 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 of anglers and guides. The months indicate the time of year when the angler usually finds the species near the coast, not a catch season. They are not official data or measurements made for this species and may vary by region and year. Legal rules appear in the rules section, with the regulation and link.
officialPortaria GM/MMA nº 1.666, de 27 de abril de 2026 — regras de proteção das espécies ameaçadas da lista nacionalArt. 3: full protection for VU, EN and CR species; § 4: incidental catch with immediate release of the live animal. The 180-day transition rule for species newly added to the list was verified from official summaries (Fiperj) and technical sources; the DOU (Brazil's Official Gazette) page did not open during verification.
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:
where are you going fishing?
Your location is saved only on this device and feeds the forecast, the map and the "today" on the home page.
