Smallest fish

What to remember

Naming the world's smallest fish depends on the rule you pick. Here the yardstick is the standard length of the smallest known mature individual, and the stout infantfish (Schindleria brevipinguis) wins with a mature male of 6.5 mm (0.26 in). Females of the species mature at 7 mm, and the largest known length is 10 mm.

The competition is tight. Paedocypris progenetica, another contender, has females mature at 7.9 mm. Photocorynus spiniceps has adult males of 6.2 mm, but they live attached to far larger females, which muddies the comparison. Judged instead by the species' maximum size, several fish, this one included, are not known to exceed 11 mm.

The stout infantfish lives off Australia, on the Great Barrier Reef and on Osprey Reef in the Coral Sea.