A strong sexual growth dimorphismof tilapiawas observed fromthe
3rd week of the experiment. Males were 18% heavier than females
when the average weight was 45 g and this difference increased to
77% when they reached the average commercial size of 350 g. Mouth
brooding females were observed from when they were 14 weeks old
and weighed 45 g; therefore energy investment by females in reproduction
can explain the early differences in size between sexes. The
differential growth between males and females is consistent with the
culture performance results and the obtained body weight growth
curves of tilapias