No feeding occurred on Sundays, following local commercial feeding practices. To minimize feed loss during delivery, all feed was distributed in circular feeding trays, equipped with a retractable cover (Plastsan Pla ´sticos do Nordeste Ltda., Caucaia,Ceara ´, Brazil) which opened in contact to the pond bottom (Nunes, 2004). Trays were allocated
at one unit per enclosure and positioned 80 cm from its internal boarder. Daily at each feeding
time, trays were rinsed, brushed clean and inspected for uneaten feed, which was then collected for weighing.