The world's smallest fish depends on the measurement used.[1]
Based on minimum standard length at maturity the main contenders are Paedocypris progenetica where females can reach it at 7.9mm,[2] [3] the stout infantfish (Schindleria brevipinguis) where females reach it at 7mm and males at 6.5mm,[1] and Photocorynus spiniceps where males can reach it at 6.2mm, but are attached to the far larger females.[4] If judging smallest based on the species' maximum size (a measurement often used for fish), Paedocypris progenetica, dwarf pygmy goby (Pandaka pygmaea), midget dwarfgoby (Trimmatom nanus) and the stout infantfish (Schindleria brevipinguis) are not known to exceed 11mm in standard length, and the two Leptophilypnion sleeper gobies are less than 10mm. A level of uncertainty about the full size range exists for some of these, as only a few specimens have been measured.
Little or no data is available on weight of most of these, but at less than 1mg it is likely that the stout infantfish (Schindleria brevipinguis) is the smallest if using this feature.[1]
| Image | Common Name | Species | Family | Standard length of smallest known mature individual | Maximum known standard length | |
|---|---|---|---|---|---|---|
| Dwarf goby | Paedocypris progenetica | Cyprinidae | 7.9mm, female | 10.3mm | ||
| Danionella translucida | Cyprinidae | 10 mm [5] | 15 mm | |||
| Danionella cerebrum | Cyprinidae | 10 mm | 12.6 mm | |||
| Leptophilypnion fittkaui | Eleotridae | ? | 9.5mm[6] | |||
| Leptophilypnion pusillus | Eleotridae | ? | 9.1mm | |||
| Pandaka pygmaea | Gobiidae | 9mm, male | 11mm | |||
| Midget dwarfgoby | Trimmatom nanus | Gobiidae | 10mm | 10mm | ||
| Photocorynus spiniceps | Linophrynidae | 6.2mm, male[7] | 50.2mm, female far larger than male and species not among smallest by maximum standard length | |||
| Stout infantfish[8] | Schindleria brevipinguis | Gobiidae | 6.5mm, male | 10mm |