potosi pupfish
Cyprinodon alvarezi
Small fish from El Potosí, in Nuevo León, Mexico, which is extinct in the wild and should not be fished.
Also called: cachorrinho-de-potosí, cachorrito de potosí, perrito de potosí, potosi pupfish
- maximum
- 5 cm
who is the potosi pupfish
Small fish of the family Cyprinodontidae, reaching 5 cm. It is endemic to El Potosí, in Nuevo León, Mexico, and lives in fresh water, between 18 °C and 22 °C, without migrating. It is not an annual fish. It is extinct in the wild and survives only in captivity, where it is hard to keep in an aquarium. Because it is so small and no longer exists free in nature, it is not a fishing species and should not be caught.
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 potosi pupfish.
fun facts
- It is hard to keep in an aquarium.
identification
Small freshwater fish, up to 5 cm, that lives only in El Potosí, in Nuevo León, Mexico. Because its range is so restricted, location is the main sign for identifying it. The body is fusiform and of ordinary form. It is not an annual fish. As it is extinct in the wild, today it can only be seen in captivity.
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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.
Essential profile: the index uses a general fish model (weather, sun, moon and tide), without a season or time of day specific to this species.
where found
Endemic to El Potosí, in Nuevo León, Mexico, in fresh water.
Habitat: Freshwater of El Potosí, between 18 and 22 °C, without migration.
rules for the potosi pupfish
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 is not dangerous. Because it is extinct in the wild, it should not be caught; if one turns up, return it to the water carefully and without handling it.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.0138, b = 3.14; 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: Cyprinodon alvarezi (ficha da espécie)Size, length-weight, depth, habitat, distribution, biology, and IUCN status. Page checked on Oct 13, 2026.
- scientific FishBase: nomes populares de Cyprinodon alvareziNames by country and language.