island trevally
Ferdauia orthogrammus · Carangidae · predator
Island jack of oceanic islands, reaching 75 cm and 6.6 kg. It appears alone, in pairs or in small schools, and is used in commercial and sport fishing.
Also called: xaréu-insular, jurel isleño, island trevally
- maximum
- 75 cm
- record/max.
- 6.6 kg
- depth
- 0–168 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
tap or drag on the chart to read each hour · on a keyboard, arrow keyssee 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 island trevally
who is the island trevally
The island jack belongs to the family Carangidae, with a spindle-shaped body compressed from the sides. It reaches 75 cm and 6.6 kg, and its common size is 40 cm. It occurs in the Indo-Pacific and, in the eastern Pacific, in Mexico, including the Revillagigedo Islands. Adults are pelagic and abundant around oceanic islands, and do not appear in coastal areas. They can be seen alone, in pairs or in small schools, near outer reefs and sandy channels in lagoons. They feed on small crustaceans that live in the sand. It is commercially fished and is also a sport fish.
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 island trevally; in the meantime, see the similar species.
fun facts
- Adults feed on small crustaceans that live in the sand.
identification
Spindle-shaped body, compressed from the sides, with the profile of a jack. Habitat matters most for identification: this is an island jack of oceanic islands, where adults are abundant, and it does not appear in coastal areas. To tell it apart from coastal jacks, such as the Pacific jack, look at where it was caught: the island jack stays around islands and outer reefs, not close to the shore.
where found
Found in the Indo-Pacific and, in Latin America, in the eastern Pacific off Mexico, including the Revillagigedo Islands.
Habitat: Oceanic waters and reefs around islands, 0 to 168 m deep.
rules for the island trevally
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 recorded danger to anglers. It is a fish up to 6.6 kg: hold it firmly by the body, avoid the mouth when removing the hook, and release it quickly.
in the kitchen
It is usually sold fresh, dried or salted.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.01318, b = 2.96; 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
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: Ferdauia orthogrammus (ficha da espécie)Size, length-weight, depth, habitat, distribution, biology, and IUCN status. Page checked on Oct 13, 2026.
- scientific FishBase: nomes populares de Ferdauia orthogrammusNames 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: