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Bragging Rights: The Smallest Fish Ever

The stout infantfish is the new holder of the title: world’s smallest vertebrate. The largest specimen found was only a third of an inch long. (Image credit: H.J. Walker)

Most people don't brag about the smallest fish they ever caught, but when it's the shortest, lightest animal in the world with a backbone, well, that's a catch for scientists.

Researchers in San Diego have identified a new species, the stout infantfish, that's the new champion of petiteness.

Six specimens were caught with very fine plankton nets in the vicinity of Australia's Great Barrier Reef, as well as in the Coral Sea. The largest of these is a mature female only a third of an inch long, which means the stout infantfish unseats the dwarf goby as the world's smallest vertebrate.

If you ordered a pound of these fish at the supermarket, you would end up taking home about a half million of them.

The record holder's nearest relative is twice as long. Like other infantfish, the new species lacks pigmentation, so it is transparent except for its eyes. It also has no teeth or scales - features characteristic of the larval stage in other fish - hence the name "infant". Researchers estimate that these remarkable fish live for only two months.

The discovery highlights the wonders that the ocean continues to reveal.

"This species expands the known size range of vertebrates and demonstrates that we still are far from knowing everything there is to know about the diversity of life," William Watson, from the National Marine Fisheries Service, told LiveScience.

Watson, one of the discoverers, stressed that ecological changes, especially in the Great Barrier Reef, could wipe out species before biologists are able to identify them.

So, are there other fish in the sea that are tinier still?

"I would not be surprised if a smaller fish is found some day," said Watson.  "I don't think it will be much smaller, however."

Michael Schirber
Michael Schirber began writing for LiveScience in 2004 when both he and the site were just getting started. He's covered a wide range of topics for LiveScience from the origin of life to the physics of Nascar driving, and he authored a long series of articles about environmental technology. Over the years, he has also written for Science, Physics World, andNew Scientist. More details on his website.