bank butterflyfish
Prognathodes aya · Chaetodontidae · omnivore
Butterflyfish of deep banks in the Gulf of Mexico, down to Yucatán, between 45 and 170 m. It is hardly seen even by divers and rarely reaches the line.
Also called: borboleta-de-banco, mariposa de banco, bank butterflyfish
- maximum
- 15 cm
- depth
- 45–170 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 bank butterflyfish
who is the bank butterflyfish
Butterflyfish of the family Chaetodontidae, with a tall, compressed body, living on deep open-sea reefs, between 45 and 170 m. It reaches 15 cm. It occurs from North Carolina and the northeastern Gulf of Mexico to Yucatán, Mexico, and is not known from the Bahamas or the Antilles. Because it lives deep, divers hardly see it. It pairs up for breeding and lays eggs in the water. It has commercial value for the aquarium trade, but is rarely fished.
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 bank butterflyfish; in the meantime, see the similar species.
fun facts
- It lives on deep reefs where divers rarely see it.
identification
Tall, compressed body, with a wide dark band sloping backward from the middle of the spiny dorsal fin to the base of the rear part of the anal fin. Unlike the shallow-water butterflyfishes of the region, such as Chaetodon ocellatus, this one lives on deep reefs, from 45 to 170 m, and the dark band is the main mark.
where found
In Latin America it is known only from Mexico, from the Gulf of Mexico to Yucatán. Its presence in the Bahamas and the Antilles is not known.
Habitat: Deep open-sea reefs, 45 to 170 m.
rules for the bank 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.
It poses no danger to the angler. Since it comes from great depth, it suffers barotrauma if it rises quickly, so release it as deep as possible.
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 aya (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 ayaNames 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: