ray
Dipturus trachyderma · Rajidae · predator
Large skate of sand and mud bottoms, from Chile to southern Brazil. It is caught more in nets and trawls than on the line, and it is threatened worldwide.
Also called: raia-de-ventre-áspero, raya vientre áspera
- maximum
- 264 cm
- depth
- 93–450 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 ray
who is the ray
The rough-belly skate belongs to the family Rajidae, the flattened-body, thin-tailed skates. It reaches 264 cm. It lives on sand and mud bottoms of the outer shelf and slope, between 93 and 450 m deep, and also appears at 20 m. It feeds mainly on bony fish and crustaceans. It is oviparous: the female lays capsules with horn-like extensions, 20 to 30 cm long, and embryos develop only with the yolk. It matures at around 13 years. In the region, it is caught mostly by bottom commercial fishing.
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 ray; in the meantime, see the similar species.
fun facts
- The egg cases are 20 to 30 cm long.
- Matures at around 13 years.
identification
Flattened skate with a wide disc, thin tail and pectoral fins attached to the head, like other skates of the family. The egg cases have horn-like extensions. To separate it from the yellownose skate, Zearaja chilensis, which also lives off the Chilean coast, look for the red or purple ocellus in the center of each pectoral, which the yellownose skate has.
where found
Lives from Chile to southern Brazil, through Argentina and Uruguay, on sand and mud bottoms.
Habitat: Sand and mud bottoms of the outer shelf and slope, 93 to 450 m deep.
coast
rules for the ray
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 (Ministerial Ordinance GM/MMA No. 1.667/2026).
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.
Large skate, threatened worldwide. Hold it by the sides of the disc, avoid the tail and release it right away, with minimal handling.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.0024, b = 3.18; 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: Dipturus trachyderma (ficha da espécie)Size, length-weight, depth, habitat, distribution, biology, and IUCN status. Page checked on Oct 13, 2026.
- scientific FishBase: nomes populares de Dipturus trachydermaNames by country and language.
- official Portaria GM/MMA nº 1.667, de 27 de abril de 2026: Lista Nacional Oficial de Espécies da Fauna Ameaçadas de Extinção (peixes e invertebrados aquáticos)The species is not on the list. Checked in the DOU of April 28, 2026.
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: