The mummichog was the first fish sent into space, aboard Skylab 3 in 1973.
The mummichog (Fundulus heteroclitus) is a small brackish-water killifish native to the Atlantic coast of North America. NASA selected it because its balance organs, or vestibular system, could help scientists study how fish orient themselves in weightlessness.
Skylab 3 launched on July 28, 1973, carrying two mummichogs and about 50 eggs. The fish were part of an experiment requested by scientist-astronaut Owen Garriott. Researchers observed how the animals adjusted when the normal gravity direction disappeared.
A common mix-up is confusing the mummichog with later space-traveling fish such as medaka and guppies. The mummichog’s claim is specifically tied to being the first fish to reach space, not the first aquatic animal or the first living organism sent beyond Earth.