Tequila Splitfin

Tequila Splitfin
Zoogoneticus tequila

Webb & Miller, 1998

Also known as: Tequila fish, Picote tequila

Max Size: Males about 4 cm SL / females to about 6 cm SL (TL up to ~7–8 cm)

A small, olive-mottled goodeid with a story as striking as its tail. Both sexes are dark olivaceous on the back and sides, fading to pale yellow on the belly, with mottling and a pair of spots at the base of the caudal fin. Reflective scales give a greenish iridescence. Males are the show: they darken — sometimes almost black — in courtship, the dorsal and anal fins pick up thin cream edges, and the caudal fin carries a broad subterminal band of red, orange, or yellow. That crescent earned them the local nickname gallito (“little rooster”). Females stay olive with clearer fins and two to four spots on the lower caudal peduncle. Males also have the classic goodeid splitfin (notched anal fin).

The species is named for Volcán de Tequila, which rises above its tiny home range in Jalisco.

Origin & Habitat
Endemic to the Río Teuchitlán / Teuchitlán Springs in the headwaters of the Río Ameca, Jalisco, Mexico (about 1,300 m elevation). It prefers shallow, quiet water (usually under 1 m) over mud, silt, sand, and rock, with little current and sparse to moderate plants (Eichhornia, Potamogeton, and similar). Water is often warm (mid-20s °C) and can be turbid.

Diet
Carnivorous. Conical teeth and a short gut point to small invertebrates — zooplankton, chironomid and other insect larvae, and microcrustaceans. In the aquarium it takes high-quality flakes and granules plus live or frozen foods such as brine shrimp, daphnia, and bloodworms.

Behavior & Temperament
Active and fairly bold. Males display, chase, and court in open water; dense plants and roots give cover and reduce stress. Best kept in groups in a planted tank with open swimming space.

Reproduction
Viviparous livebearer. Sexual maturity can be reached in 6–10 weeks under warm aquarium conditions. Broods typically number 10–29 young (fewer in a female’s first year). Breeding is seasonal in nature, peaking in warmer months.

Conservation Status
IUCN: Endangered (EN) — population now increasing.
Mexican NOM-059: En Peligro de Extinción.

This is one of the great goodeid comeback stories. The species was already thought extinct in the wild when it was formally described in 1998. A tiny remnant (fewer than 50 adults in a pool only a few meters across) was found around 2001, then lost again. Captive stocks — built by hobbyists, zoos, and universities — saved it. From 2014–2017, Universidad Michoacana, Chester Zoo, the Goodeid Working Group, and local partners acclimated fish in outdoor ponds and released them back into the Teuchitlán Springs after removing many non-natives. Wild-born young appeared the following year, and the fish have since spread into nearby springs. Ongoing monitoring and invasive-species control remain essential.

A dark little “rooster” with an orange tail crescent, named for the Tequila volcano — and living proof that a species once written off can be brought home.