4. Discussion
Castration in Mozambique tilapia decreased circulating levels of
androgens in 90% for T and almost in 100% for KT (to below 100 pg/
ml). Concomitantly, courtship behavior, nest building and nuptial
coloration were abolished in castrated males, whereas aggressive
behavior was not significantly affected. The data from the urinary
bladder males confirms the effect of castration on androgens since
males from this treatment were similar to those of the sham operated
group.
The reduction of androgen levels in castrated males has been
previously demonstrated in many species and confirms role of
the testis as the main source of androgens in tilapia. The extinction
of the whole set of reproductive behaviors (i.e. nuptial coloration,
nest building and courtship) in castrated males that experience a