Development and identification of the ricefish Oryzias in Thailand

Abstract

Ricefish larval specimens were collected from breeding tanks and rearing ponds. The larvae were divided into 3 developmental stages i.e. larval, post-larval, and juvenile stages, and their morphometric and meristic characters, as well as chromatophore pigment patterns were studied. The chromatophore pigment pattern, number of myomeres, dorsal fin rays and anal fin rays were characteristics used for species identification. For Oryzias larvae, the chromatophore pigmentation on the gut, midline, and dorsal and ventral parts of the body were important characteristics. The caudal, dorsal, and anal fin rays were also the characteristics used in the case of identifying the juvenile fish. Using the above criteria, four species of ricefish, i.e. O. javanicus, O. dancena, O. mekongensis, and O. minutillus, were identified.