Pike Top Minnow Breeding Guide

Breeding the predatory livebearer Belonesox belizanus: sexing by size and gonopodium, conditioning on live prey, large broods of up to 100 and protecting predatory fry from cannibalism.

Overview

Belonesox belizanus, the pike top minnow or pike killifish, is the sole member of its genus and a highly specialized predatory poeciliid. FishBase records it from Laguna San Julian near Ciudad Veracruz in Mexico south along the Central American coast to Nicaragua, with an introduced population in Florida. It is a non-migratory, demersal fish of weedy canals that tolerates poorly oxygenated water. Unlike most poeciliids it is piscivorous, taking very large prey for its size with an extremely flexible upper jaw. It is a livebearer and, by poeciliid standards, not an easy aquarium resident.

Sexing

Females are considerably larger than males: FishBase gives males to 20 cm total length and females to 15 cm, with a common length of about 9.7 cm. The body is elongated with a flat back and an upturned lower jaw longer than the upper. Males possess a gonopodium, the modified anal fin used to transfer sperm.

Conditioning

As an obligate piscivore the species must be conditioned on live or meaty prey; FishBase records it occupying weedy canals and tolerating poorly oxygenated waters. It accepts a wide range, from 25-37 °C, pH 6.0-8.0 and hardness 9-19 dH, and tolerates salinity up to 40 ppt, so brackish maintenance is possible.

Mating & Gestation

Fertilization is internal via the gonopodium. As a livebearer it produces large broods; FishBase reports up to about 100 young per cycle. Pairing should be done cautiously given the predatory nature and the size difference between sexes: a male is much smaller than a female and should be introduced to a well-fed female to reduce the risk of aggression.

Birth & Fry Care

Fry are born live and, like the adults, are predatory; cannibalism is documented in Belonesox and related livebearing genera, so fry must be separated from adults and from larger siblings. Newly born fry require small live foods of appropriate size to grow on.

Common Challenges

This is a species-tank predator that eats other fish and even its own fry, so dedicated grow-out space and a steady supply of live food are essential. Resource competition at high density increases cannibalism, making generous space and feeding important.