2. Material andmethods
The experiment was carried out at the Aquaculture Research Station
CINVESTAV-Merida, from April to September 2011. Juveniles of Nile
tilapia Stirling strain (Scotland, UK) were produced at the research station.
A naturalmixed tilapia fingerling population was isolated 5 weeks
after hatching and fed a commercial tilapia formulated diet with 42%
crude protein, 4 times daily to satiation, until they reached 22 g in
average. At this stage, juveniles were hand-sexed and sorted into
male and female groups. Male and female juveniles of 24 g on average
(11 weeks after hatching) were selected and distributed in the
experimental tanks. Native juveniles of the Mayan cichlid were
obtained from the ornamental fish enterprise Enmanuel (Merida,
Yucatan, Mexico