A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Aquaculture and Aquatic Resources Management, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 2014

A four-week trial on nursing of Nile tilapia fry was conducted at the Asian Institute of Technology, Thailand to compareamong the three stocking densitiesi.e. 500, 1,000 and 1,500 per 100 L tankin aquaponic system with lettuce (Lactuca sativa L.). Eachaquaponic system included a fish tank (100 L), a vegetable grow-bed (1 m2surface x 0.15 m water column) and a gravel bio-filter. The experiment consisted of three treatments in threereplicates. The first set of replicatesof all the treatment was carried out in first fourweeks period, and the second andthethird werecombinedin the following 4 weeks. Monosex tilapia fry of initial size 0.2 g were nursedin theaquaponicsystem with 9 lettuce plantsgrown in a floating raft in a grow-bed. The frywerefed with commercial feed (30% Protein content) three times daily usingfeeding rate gradually reduced from 10 to 7 % total weigh day-1following the increasing fish biomass. Results showed that there were significant differences among treatments in growth rate, feed conversion ratio and tilapia fry production (P < 0.05) but not in survival rate (P > 0.05). The fry grewfaster (5.32 ± 0.04 % day-1and 5.28 ± 0.04 % day-1respectively) when stocked at 500 and 1000 per tank densities as compared tothat at 1,500with 4.44 ± 0.10% day-1. FCR in Treatment3 was significant higher than that in Treatment2 and Treatment1 (2.01, 1.22 and 1.19 respectively) (P < 0.05). However, mean survival rate of each treatment were not significant different. It varied from 84.4 ± 2.0(%) in Treatment3 to 87.9 ± 1.2(%) in Treatment2. With regards to lettuce, the mean growth rate of lettuce in Treatment3 (12.5% day-1)and the Treatment2 (12.3 % day-1) werecomparable. However, the growth rate of lettuce in Treatment 1 was the lowest (10.8% day-1) (P < 0.05). Similarly,biomass yield of lettuce in Treatment3 (1.1kg)were comparable in Treatment2 (0.9 kg).These bothwere significantly higher than that in Treatment1 (0.6 kg). The highest profit (20.5%)was obtained from Treatment2 (110 Baht), which was significantlyhigher than the returncame from Treatment3 (58 Baht) and negative gain in Treatment1 (115 Baht).Therefore, it a density of 1000 fry per 100 litre of water is recommended. However, farmers have to use larger tanks of approximately 2,000 litre capacity and stock and sell 20,000 fry each month so that he/she can generate adequate income to support a family.