scythemarked butterflyfish
Prognathodes falcifer · Chaetodontidae · omnivore
Solitary butterflyfish of reefs and rocky areas in the eastern Pacific, from 10 to 150 m deep. It rarely reaches aquariums, because it lives in deeper water.
Also called: borboleta-de-foice, mariposa guadaña, scythemarked butterflyfish
- maximum
- 15 cm
- depth
- 10–150 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
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 scythemarked butterflyfish
who is the scythemarked butterflyfish
Butterflyfish of the family Chaetodontidae, with a tall, disk-shaped, compressed body. It reaches 15 cm. It lives on rock areas and reef boulders of the eastern Pacific, from southern California to Peru, including the Galápagos, from 10 to 150 m. It is usually solitary and forms pairs during breeding. It feeds on crustaceans, worms and small invertebrates. It has commercial use, but since it lives in deeper water it is seldom collected and rarely seen in aquariums.
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 scythemarked butterflyfish; in the meantime, see the similar species.
fun facts
- Close relatives pull the tube feet off sea urchins and eat them.
identification
Tall, compressed, disk-shaped body, with a short, deep profile, like all butterflyfish. The common name, sicklefin butterflyfish, refers to a sickle-shaped mark on the body. The habitat helps tell it apart: this species lives from 10 to 150 m, in areas with boulders, and is usually seen alone, deeper than other eastern Pacific butterflyfish, such as the blacksnout butterflyfish (Johnrandallia nigrirostris).
where found
Eastern Pacific of Latin America, in Mexico and Ecuador, including the Galápagos, in rocky areas from 10 to 150 m.
Habitat: Areas with boulders and rocks on reefs, from 10 to 150 m deep.
rules for the scythemarked butterflyfish
Summary of the regulations we found, with the source for each. Rules change; before keeping or transporting fish, check with the state environmental agency.
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.
No danger to anglers has been recorded. It is a small fish of deep waters: handle it with a wet hand and return it to the water carefully.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.02239, b = 3.01; FishBase (relação peso-comprimento bayesiana, estimativa)). 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: Prognathodes falcifer (ficha da espécie)Size, length-weight, depth, habitat, distribution, biology, and IUCN status. Page checked on Oct 13, 2026.
- scientific FishBase: nomes populares de Prognathodes falciferNames by country and language.
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: