Integrated multi trophic aquaculture of red tilapia (Oreochromis sp.) fairy shrimp (Streptocephalus Sirindhornae) and lettuce (Lactuca Sativa) in recirculation system | |
| Author | Pakamas Sreejariya |
| Call Number | AIT Diss. no.AQ-16-01 |
| Subject(s) | Aquaculture Red Tilapia Aquaponics |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Aquaculture and Aquatic Resources Management |
| Publisher | Asian Institute of Technology |
| Abstract | This research was aimed at identifying parameters that could improve the profitability of an aquaponic system, either by reducing its operating cost or by increasing its revenue. The first experiment was aimed at determining the optimum density of fairy shrimp in a small-scale aquaponic system. Four treatments were tested using different fairy shrimp stocking densities: 15, 30, 45, and 60 ind. L-1, respectively. Each treatment had three replicates. The culture system consisted of two aquariums units; one with red tilapia and the other with fairy shrimp. Nutrient-rich water from fish aquarium was pumped to the fairy shrimp aquarium using a small electric pump. The results showed that the survival of fairy shrimp was low but the highest was obtained at a stocking density of 30 ind. L-1(55%) whereas at stocking densities of 45 and 60 ind. L-1 it was the lowest (26% and 11%). The second experiment was aimed at comparing different lettuce varieties in regard to their impact on water quality and growth of red tilapia and fairy shrimp in an aquaponic system. Three locally available varieties of lettuce were tested: “green oak”, “green cos” and “butterhead”. After six weeks of experiment, lettuce performed well in the aquaponic system, as significant differences were observed between the control (no lettuce) and the treatments with different varieties. However, no significant difference was observed among varieties, whether in terms of water quality or growth and survival of tilapia and fairy shrimp. All fish survived whereas fairy shrimp survival was very low with 23-28% survival in treatments that included lettuces vs. 19% in the control. The third experiment was aimed at determining the impact of water recirculating duration on lettuce growth and nitrate content in a commercial-scale aquaponic system. Three water recirculating durations times consisted of 11h at daytime, 13h at nighttime and through 24h were tested for an aquaponic system of red tilapia and lettuce. The water recirculation interruption, either during daytime and night-time, did not affect the lettuce growth, thus offering the possibility to increase aquaponics profitability by reducing the operational cost of pumping for water recirculation. In this case, technical recommendation can be based on economic considerations such as the differential prices of electricity during day and night. The nitrate concentration in the sap of the leaf midribs was in accordance with local (EU) regulations in all treatments. The fourth experiment was aimed at determining the effect of shading on lettuce growth and nitrate content in a commercial-scale aquaponic system. The shading rates of 30, 60% and no shading (control) were tested. The results showed that shading did not affect nitrate content in the sap of the leaf midribs. The optimum lettuce growth was observed for shading 30%, followed by no shading (control) and shading 60%. Shading 60% also affected lettuce shape by maximizing height and minimizing diameter of lettuce plant. Based on this data, shading at a rate of 30% should be selected for growing lettuce in an aquaponic system of red tilapia, which is in accordance with the EU maximum permissible leaf nitrate concentrations in vegetables for human consumption. Overall, this dissertation showed that profitability of farming red tilapia in the recirculating system could be increased by integrating with fairy shrimp and lettuce. Stocking density of fairy shrimp at 30 ind. L-1 was suitable for the system without additional feeding. Also, butterhead variety was the best for the system because it provided both benefits of relatively high yield and water quality control. In case of reducing production cost, water recirculation time could be restricted to 12 hrs without negative impacts on lettuce growth, especially operation should be done on nighttime is electricity cheap in the nighttime for saving cost. Another way for reducing cost was shading the lettuce at the maximum rate of 30% because it improves lettuce growth and maintained lettuce tree shape. |
| Year | 2016 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Aquaculture and Aquatic Resources Management (AQ) |
| Chairperson(s) | Yakupitiyage, Amararatne; |
| Examination Committee(s) | Annachhatre, Ajit P.;Anal, Anil Kumar;Silva, Sena Susantha De |
| Scholarship Donor(s) | Rajamangala University of Technology;Royal Thai Government Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2016 |