Small, slender shark of mud and sand bottoms, hunting crabs and shrimp from the Gulf of Mexico to Venezuela and southern Brazil. Near Threatened worldwide. Not on the Brazilian list, but Mustelus are easily confused: when in doubt, release it.
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 narrowfin smooth-hound
overview
who is the narrowfin smooth-hound
The narrowfin smooth-hound lives on the continental shelf over mud and sand bottoms, from 1 to 100 m and usually between 3 and 40 m. It eats crabs and shrimp, as well as bony fish. It is viviparous, with a yolk-sac placenta, bearing 7 to 14 pups per litter, born at about 30 cm. It occurs in the western Atlantic, from Florida and the northern Gulf of Mexico to Venezuela, and also in southern Brazil. IUCN considers it Near Threatened (2019). It is not on the Brazilian national list, but other Mustelus are and look very similar, so it is best to release it. In other countries it is a small commercial fishery resource and a sport fish (FishBase).
fun facts
The English name narrowfin smooth-hound is also used as Florida smooth-hound (FishBase).
In Cuba and other countries, its common names ("boca dulce", "viuda") get mixed up with those of M. canis.
Born at about 30 cm (FishBase).
how to recognize it
identification
Small, slender smooth-hound with a pointed snout and no spines on the dorsal fins, like other Mustelus. The differences from the smooth dogfish (M. canis) are subtle and require examining the animal in hand; FishBase warns that similar species in the region are confused with M. canis. In practice, in the field, treat it as a "Mustelus" and follow the most restrictive rule: in Brazil, the smooth dogfish (EN), the canejo smooth-hound (M. fasciatus, CR) and the Brazilian smooth-hound (M. schmitti, CR) are protected.
beach: 12' to 14' for a 100 to 150 g sinker; boat: 6' to 7', 15 to 30 lb
spinning / baitcasting reel
5000 to 7000 spinning reel
line
monofilament 0.35 to 0.45 mm
leader
monofilament 0.60 mm
hook
circle hook 2/0 to 4/0, preferably barbless
natural baits
shrimp
lula
fish fillet
caranguejo
accessories
cutting pliers
long-handled hook remover
luvas
tip from an angler
In Brazil, release every Mustelus shark: the protected species cannot be told apart from the others by appearance alone.
what the law says
rules for the narrowfin smooth-hound
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 (Portaria GM/MMA nº 1.667/2026). Global: Near Threatened (NT, A2bd), assessed on Jun 21, 2019 (IUCN, via FishBase).
Brazil: this species is not on the list, but other Mustelus sharks are
release every Mustelus; M. canis, M. fasciatus and M. schmitti are protected
The narrowfin smooth-hound (Mustelus norrisi) is not on the national list (Portaria GM/MMA nº 1.667/2026). Three other Mustelus are: M. canis (EN), M. fasciatus (CR) and M. schmitti (CR), with catch, transport and trade banned (Portaria GM/MMA nº 1.666/2026, art. 3). Because Mustelus are easily confused and field identification is uncertain, treat every shark from this group caught in Brazil as protected and release it in the water. Incidental catch with immediate release of the live animal is not an offense (art. 3, § 4).
Finning prohibited: shark only whole, with its fins
fins naturally attached to the body
Finning is banned in Brazil (catching sharks and rays and keeping only the fins, discarding the rest of the body). The rule covers landing, transport and trade by fishing vessels: every shark or ray must arrive with its fins naturally attached to the body (partial cutting to fold them against the body is allowed); it is forbidden to carry on board an animal without fins or with loose fins, and to transfer sharks and rays between vessels.
1 specimen per angler per day (counts as 5 against the quota of 10)
In recreational sport fishing in Mexican marine waters, the shark limit is one specimen per angler per day, which counts as five toward the total limit of ten fish (no more than five of the same species). Specimens beyond the quota may only be released alive, in good survival condition (catch and release), and sport-caught fish may not be sold. Sport fishing is also not allowed in closed zones and seasons or in protected natural areas without the proper permits. For NOM-017, Mustelus sharks are listed as "tiburón".
Mexico: NOM-029-PESC-2006 regulates commercial shark and ray fishing
NOM-029 is the rule for shark and ray fishing at commercial scale: it applies to holders of permits for directed fishing of these animals and to those who catch them by chance (section 1.2), and covers commercial fishing vessels (section 4.2.1); sport fishing has its own rule, NOM-017. It prohibits keeping only the fins of sharks (section 4.2.1) and provides closed seasons and closed zones, set by notice in the DOF, for directed fishing (sections 4.2.3 and 4.3.4: no directed fishing during closed seasons, within 5 km of coral reefs, in front of river mouths and lagoons, in front of turtle nesting beaches, and near sea lion colonies). The species is listed in Normative Appendix A, on the Gulf of Mexico and Caribbean Sea shark list ("tiburón mamón").
Mexico: annual closed seasons for sharks and rays (check the dates for the year)
confirm with the agency
NOM-017 (item 4.10 a) prohibits recreational fishing in closed zones and seasons, and NOM-029 (item 4.2.3) requires the authority to set closed seasons for sharks and rays by notice in the DOF; the dates change and vary by coast. On Aug 1, 2025, the Secretaría de Agricultura and Conapesca announced, for the Pacific coast, the use of sharks and rays from August 1 to April 30 (May to July are excluded, our interpretation from the announcement) and, in Tabasco, Campeche, and Yucatán, a closed season from August 1 to 29. We did not find the official notice in force in 2026: confirm the dates with Conapesca before fishing.
Colombia: marine sharks and rays are not fishery resources
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.
Panama: sharks and rays may not be caught in recreational fishing
catch, retention, and landing banned (from about Dec 10, 2026)
Executive Decree 9/2026 (art. 19) bans, throughout the national territory and in sport, recreational, or tourism fishing, the catch, retention, handling for recreational purposes, use, and landing of sharks and rays (subclass Elasmobranchii). If one is hooked by accident, it must be released immediately, without taking it fully out of the water and without unnecessary handling. It is also prohibited to promote them as targets in tournaments (art. 19) and to sell the catch (art. 20). The decree takes effect six months after its promulgation on June 10, 2026 (art. 40), around Dec 10, 2026, and repeals Resuelto ADM/ARAP 002/2012 (art. 39). Confirm the date with ARAP.
North CoastNortheast CoastSoutheast CoastSouth Coast
Many sharks and rays are on the national list (CR, EN or VU), with catching, keeping and transport prohibited, including those listed here. Species added to the list only in 2026 follow the 180-day deadline (until about Oct 25, 2026). If unsure of the species, release it.
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.
Remove the hook with a dehooker while it is still in the water, or with the animal wet, holding it by the body and away from the mouth, and release it quickly. It is small and handles quick release well. In Brazil, always release it.
in the kitchen
FishBase records small-scale commercial fishing. Because other Mustelus sharks are protected in Brazil and identification is uncertain, the good practice is to release it.
calculator
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.00174, b = 3.1; 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
The seasonal weights (months), the time of day, the sensitivities (cold, pressure, moon, wind, rain, tide, strong light, murky water and noise), the water temperature range and the common size range are the app's editorial estimates, supported by FishBase and by the literature cited below, with no measurements of our own for this species. The months show when an angler may find the species near the coast, not a catch season. They are not official data and may vary by region and year. Legal rules appear in the rules section, with the norm and a link.
officialPortaria GM/MMA nº 1.666, de 27 de abril de 2026: regras e restrições para as espécies ameaçadas da lista nacionalArt. 3: full protection for EW, CR, EN, and VU species (catching, transporting, storing, holding, handling, processing, and trading are banned); § 4: the restriction does not apply to incidental catch when the animal is released alive; art. 12: for species added to the list by a new ordinance, the art. 3 bans start 180 days after publication. Text checked in the DOU on Oct 13, 2026.
officialMéxico: NOM-029-PESC-2006, pesca responsável de tubarões e raias (DOF de 14/02/2007)Copy of the text published in the DOF, on the standardization platform of the Secretaría de Economía. Items 1.2, 4.2.1, 4.2.3, and 4.3.4 and Normative Appendix A checked on Oct 13, 2026. The standard was written for commercial fishing; recreational fishing has its own standard, NOM-017.
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.
