The kotso (Paretroplus petiti) is a species of cichlid fish from northwestern Madagascar. Currently rated as data deficient by the IUCN, this species is virtually unknown. The only known specimen is a juvenile that was collected more than 80 years ago.[1] It is not entirely clear where it was collected, but likely from the Maintimaso River or Lake Ambanja, which both are part of the Betsiboka River drainage.[1] Erroneously, the name P. petiti has often been applied to members of a different species, P. dambabe.[1] The specific name honours the French zoologist and anatomist Georges Petit (1892-1973) of the Muséum national d’Histoire naturelle, who collected type.[2]