CR

Bighead Pupfish

Cyprinodon pachycephalus

Declining

Overview

The bighead pupfish, known in Spanish as cachorrito cabezon, is a critically endangered species of pupfish in the family Cyprinodontidae. It is endemic to an area covering less than 1 km2 (0.4 mi2) at San Diego de Alcala in the Conchos River basin, Chihuahua of Mexico. It lives in hot springs, their outflows and an impoundment pool in water that ranges at least from 25 to 49 °C (77–120 °F).

Cyprinodon pachycephalus faces severe threats from habitat modification and water extraction in its extremely limited desert spring systems. The species is vulnerable to groundwater pumping that reduces spring flow, while introduced species and habitat degradation from human activities further compromise its survival. Climate change poses an additional long-term threat through increased temperatures and altered precipitation patterns affecting already fragile spring ecosystems.

Threat summary

Habitat

This critically endangered pupfish is endemic to isolated desert springs and associated pools in arid regions of Mexico. It inhabits shallow, warm spring-fed waters with specific temperature and salinity requirements that have remained stable over thousands of years.

Artificial - Aquatic & marine· majorWetlands (inland) - Permanent rivers/streams· major

Other threatened species in CYPRINODONTIDAE

Hispaniola PupfishEN

Hispaniola Pupfish

Cyprinodon bondi

Unknown
VU

Andean Killfish

Orestias munda

Declining
VU

San Ignacio Pupfish

Cyprinodon bobmilleri

Unknown
VU

Kissing Pupfish

Cyprinodon suavium

Unknown

Threatened in Mexico

EN

Turbinicarpus horripilus

Declining
CR

Turbinicarpus mandragora

Declining
EN

Opuntia pachyrrhiza

Declining
EN

Arachnothryx tacanensis

Declining

Frequently asked questions

Why is Bighead Pupfish classified as Critically Endangered?
Bighead Pupfish is classified as Critically Endangered — facing an extremely high risk of extinction in the wild — because population sizes are very small, declining sharply, or restricted to a tiny range. Cyprinodon pachycephalus faces severe threats from habitat modification and water extraction in its extremely limited desert spring systems. The species is vulnerable to groundwater pumping that reduces spring flow, while introduced species and habitat degradation from human activities further compromise its survival. Climate change poses an additional long-term threat through increased temperatures and altered precipitation patterns affecting already fragile spring ecosystems.
Where does Bighead Pupfish live?
Bighead Pupfish occurs in Mexico. Country-level distribution data is sourced from the IUCN Red List and cross-referenced with GBIF occurrences.
What are the main threats to Bighead Pupfish?
The main threats to Bighead Pupfish are ai-1, ai-2, ai-3, and ai-4. The full IUCN-classified threat record for this species is detailed on the species page.

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