Table 2 Description of maturity stages of female O. niloticus as adopted from Mous et al. (1995)

Stage I: Immature: Appearance like testes; sexes indistinguishable macroscopically

Stage II: Early developing: Ovaries to be recognized by small whitish dots (eggs); caudal part of the ovaries more thickened than the rostral part

Stage III: Developing or recovering: Eggs developing inside the ovaries unequal in size

Stage IV: Early ripening: Eggs equal in size but not fully grown; all coloured yellow

Stage V: Ripe: Eggs large and ovaries visible from the ventral side of the cavity

Stage VI: Spent: Eggs or juveniles in the buccal cavity; ovaries recovering, thin and reddish; eggs unequal in size, often including a few residual stage V eggs