Eastern Mosquitofish
Gambusia holbrooki
Least Killifish
Heterandria formosa
About
The least killifish is one of the smallest freshwater fish in the world. It is a tiny olive-coloured fish that gives birth to live young, a type of fish called a livebearer. It spends its life tucked among plants in quiet southern waters.
Also known as: dwarf top minnow, mosquitofish
How to tell it apart
Very few native freshwater fish sharing its plant-filled home grow this small. Its tiny size alone is often the easiest way to know it.
Appearance
Its body is olive-coloured with a dark stripe running lengthwise through the middle. There is a dark spot on the back fin, called the dorsal fin, and females carry a second dark spot on the fin near the tail, called the anal fin, that males lack. In males, that fin near the tail is changed into a thin, rod-like part used to mate with females.
Habitat
It lives in the southeastern United States, from North Carolina south through Georgia and Florida and west along the Gulf Coast to Louisiana, with recent finds as far as eastern Texas. It likes quiet, plant-filled fresh water that barely moves, though it can also handle brackish water, water that is part fresh and part salty.
Breeding
Like its livebearer relatives, the least killifish fertilises eggs inside the female's body. The young grow inside her until they are born able to swim. Unlike most livebearers, which release a whole brood at once, this species lets its young go a few at a time over a long period.
Did you know?
It was once ranked the seventh smallest fish species in the world, and it remains the smallest fish species found in North America.
Log it in Into the Blue
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