SUITABILITY OF COMMUNAL REARING FOR PERFORMANCE TESTING OF TILAPIAS

Triplicate plastic pools were stocked separately with either Tilapia aurea, T. hornorum, T. nilotica, or Taiwanese red tilapia fingerlings (60 fish/pool) averaging 7.3, 5.7, 8.2, or 7.6 g, respectively. Three other plastic pools were stocked communally (mixed groups) with equal numbers of similarly sized fish of the above four groups. Fish were fed 32% protein sinking pellets at an initial rate of 5% and decreasing to 3.5% total body weight daily divided into two equal feedings. All the fish were harvested after 88 days. Gains in weight and total length for separately stocked pools were 62.8 g (78.8 mm), 59.8 g (79.0 mm),69.8 g (80.7 mm), and 73.5 g (86.0 mm); and for communally stocked pools were 64.6 g (77.2 mm), 61.5 g (79.5 mm), 70.6 g (81.7 mm), and 91.0 g (89.4 mm) for T. aurea, T. hornorum, T. nilotica, and Taiwanese red tilapia, respectively. Males gained more than females for all groups in separate and communal cultures, however, a significant group by sex interaction existed. In separately stocked pools, males gained 23, 119, 76 and 43% more in weight, and 12, 59, 35 and 21% more in length than females for T. aurea, T. hornorum, T. nilotica, and Taiwanese red tilapia, respectively. Rankings of gains were the same for separately and communally stocked pools indicating that communal rearing is an efficient means of performance testing tilapias