slender thread herring
Opisthonema bulleri · Dorosomatidae · forage fish
Pacific thread herring, with a spindle-shaped body, less abundant than the others of its genus in the region. It is taken in subsistence fishing.
Also called: sardinha-de-fio-esguia, arenque de hebra, machete del norte, pinchagua, slender thread herring
- maximum
- 20 cm
- depth
- 0–50 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 slender thread herring
who is the slender thread herring
A sardine of the family Dorosomatidae, with a spindle-shaped, compressed body and the long filament at the end of the dorsal fin, a trait of the genus. It reaches 20 cm, and its common size is 18 cm, measured without the tail. It forms schools and lives from Baja California, Mexico, to Peru, in coastal and shelf waters down to 50 m. It is the least abundant of the genus's sardines in the eastern Pacific. It eats crustaceans and pteropods, small planktonic snails. It is taken in subsistence fishing, almost always together with other thread herrings.
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 slender thread herring; in the meantime, see the similar species.
fun facts
- It is the least abundant of the genus's sardines in the eastern Pacific.
identification
Spindle-shaped, compressed sardine with the long filament at the end of the dorsal fin, a trait of the genus. In the same region, the Pacific thread herring (Opisthonema libertate) and the middle thread herring (Opisthonema medirastre) are of the same genus and look alike; among the three, the safe separation is by gill rakers, which are fewer in this species. The middle thread herring also has a dark spot behind the gill slit and a yellow band on the flank.
where found
From Baja California, Mexico, to Peru, in coastal Pacific waters.
Habitat: Coastal and shelf waters, in schools, down to 50 m deep.
rules for the slender thread herring
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.
Harmless. It almost never shows up on the line; it is a fish with delicate skin that goes into subsistence nets: handle it with a wet hand.
in the kitchen
It is caught in subsistence fishing, for local consumption.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.00871, b = 3.06; 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: Opisthonema bulleri (ficha da espécie)Size, length-weight, depth, habitat, distribution, biology, and IUCN status. Page checked on Oct 13, 2026.
- scientific FishBase: nomes populares de Opisthonema bulleriNames 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: