Abstract
Thirteen-day-old tilapia larvae (mean weight: 0.01 g), at the onset of exogenous feeding, were stocked at five fish per liter in rearing tanks. They were fed unialgal cultures of Spirulina platensis from varying ages [0, 12, 17, 21, and 28 days after the onset of exogenous feeding with a standard length (SL) of 0.8 cm, 1.8 cm, 2.0 cm, 2.5 cm, and 3.0 cm, respectively]. Feeding experiments on larvae fed different amounts of raw Spirulina were also designed. Acceptability tended to improve with an increase in the initial SL of the experimental larvae, and larval tilapia from 2.0 cm SL showed significantly rapid growth when fed raw Spirulina. Larval tilapia that were fed solely raw Spirulina at a feeding rate of 30% (on a dry basis) of bodyweight in the first 3 weeks, 10% in weeks 4-6, and 3% in weeks 7-10, kept growing without any abnormality. Final weight and SL reached 3.2 ± 0.4 g and 4.5 ± 0.2 cm (n=20), respectively, demonstrating that raw Spirulina was accepted by tilapia even just after the onset of exogenous feeding. Growth and survival rate of larvae fed Spirulina at different feeding rates in the first 3 weeks just after the onset of exogenous feeding showed a significant difference. Larval tilapia fed to satiation had the best growth performance throughout the 10-week rearing period, whereas those fed at a feeding rate of 10% stopped growing eventually and stunting was found. The availability of an abundant supply of Spirulina during the early stages seemed to be important for the normal growth and development of tilapia. Raw Spirulina appears to be an effective uni-feed for larval tilapia when developing a food chain of phytoplankton-fish for a closed ecological recirculating aquaculture system (CERAS).
