Stomach content, gut length, morphology of pharyngeal teeth and gill rakers of
Oreochromis shiranus larvae and juveniles were investigated in order to elucidate
the timing of feeding habit conversion, and the relationships between feeding habit and
the feeding-related morphological characters. Stomach content showed that the feeding
habit of fish drastically changed between 14-20 mm TL from zooplanktovorous to herbivorous
(phytoplanktovorous). Pharyngeal plate and teeth were already ossified in the smallest
fish of this study (9.95 mm TL) and teeth number increased as fish grew. Percentage
length of gut ((gut length/TL) x 100 %) became more than 100 % when TL reached 15-20 mm,
falling mostly under the size with feeding habit conversion. Gill rakers in 4th gill arch
started appearing at 14 mm TL when the feeding habit started converting. Consequently, the
conversion of feeding habit in Oreochromis shiranus started when the percentage
intestine length became over 100 % and gill rakers in 4th gill started appearing, and
pharyngeal teeth did not seem to relate directly with such feeding habit conversion.