An integrated rotation culture system for fattening large Nile tilapia (Oreochromis niloticus) in cages and nursing small Nile tilapia in open ponds | |
| Author | Yang, Yi |
| Call Number | AIT Diss. no.AS-97-02 |
| Subject(s) | Nile Tilapia Fish-culture Fish ponds |
| Note | A dissertation submitted in the partial fulfillment of the requirements for the degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AS-97-02 |
| Abstract | This study was conducted to develop a tilapia-tilapia cage-cum-pond integrated rotation culture system for fattening large Nile tilapia (Oreochromis niloticus) stocked in cages which were suspended in ponds where small Nile tilapia were nursed utilizing wastes derived from cages This system is to achieve higher economic benefits and waste recycling. A series of six experiments were conducted at Asian Institute of Technology, Thailand to; 1) determine the appropriate stocking densities and biomass of both caged and open-pond Nile tilapia for optimal growth and water quality; 2) investigate nutrient dynamics and utilization efficiency in this system, 3) determine the effects of top-¬surface to volume ratios of cages on growth performance of caged Nile tilapia; 4) compare pond production efficiency between the integrated culture system and the mixed pond culture system, 5) determine the effects of aeration on the carrying capacity of Nile tilapia in terms of production of both caged and open-pond Nile tilapia and water quality; 6) develop bioenergetics growth models for Nile tilapia in both cages and in open-pond in the integrated rotation culture system. The experiments were conducted in fifteen 330-m3 ponds with a randomized complete block design. Fish used for all experiments were all males Nile tilapia sex-reversed by methyl-testosterone treatment in fry stage. Large size tilapia (86-159 g) were confined in 4-m3 net cages in ponds and fed with commercial floating pellets (crude protein 30%) twice daily, five or six days per week. Feeding rates were 3%, 2.5% and 2% body weight per day during the first, second and third month, respectively. Smaller size tilapia (13-58 g) were nursed in the open pond, feeding solely on natural foods derived from cage wastes. The experimental period for each trial ranged from 86 to 90 days. Tilapia stocking density in cages had significant (P < 0.05) effects on survival, growth and feed conversion ratio of caged tilapia, and on growth of open-pond tilapia. Growth performance of caged tilapia increased as stocking density increased from 30 to 50 fish/m3 and decreased significantly (P < 0.05) when the stocking density increased beyond 50 fish/m3. The present experiment shows that the optimal stocking density for caged tilapia is 50 fish/m3 with a total of 200 fish/pond. Growth performance of caged tilapia decreased significantly (P < 0.05) with the number of cages increased from 1 to 3 per pond. Fish yield in each cage leveled off with increasing tilapia biomass in each cage, indicating that the carrying capacity of caged tilapia might be exceeded. Among all treatments, the highest net fish yield in cages was achieved in the treatment with 2 cages per pond, but the final size did not reach the desirable market size (>500 g). The net fish yield of smaller tilapia stocked at 2 fish/m3 in open ponds ranged from 1.14 t/ha/3 month for the treatment with 1 cage per pond to 2.22 t/ha/3 month for the treatment with 3 cages per pond. The carrying capacity and growth performance of caged tilapia could be enhanced significantly (P < 0.05) by lowering the stocking density in open ponds from 2 to 1.4 fish/m3 in the treatment with 2 cages per pond. The analyses of nutrient budgets for a 3- month culture cycle indicated that cage wastes contained 2.78, 5.30 and 7.12 kg N and 0 55, 1.14 and 1.59 kg P in the ponds with 1, 2 and 3 cages, respectively, which were recovered by the tilapia in open ponds at 29.31, 26.53 and 21,91% N and 40.89, 34.60 and 27.16% P, respectively, As dissolved oxygen was shown to be the most critical factor limiting fish yield in cages, it was demonstrated that the carrying capacity could be enhanced by aeration for 5 hours at nighttime. An tilapia-tilapia cage-cum-pond integrated rotation system has been developed through the present experiments. As demonstrated, large size tilapia (around 140 g) can be stocked at 50 fish/m3 in two 2x2x1.2-m cages suspended 1 m deep in 330-m3 earthen ponds with water depth of 1.2 m, where smaller size tilapia (around 20) are stocked at 1.4 fish/m3 outside the cages. In each culture cycle of 3 months the caged tilapia can be fattened to 500 g size and the small tilapia nursed in the open ponds can be removed to restock the cages. Two bioenergetics growth models were developed for Nile tilapia in fertilized ponds and in the integrated culture system, respectively. The models linked growth of Nile tilapia at large with limiting nutrients in pond water. The models incorporated five key variables affecting Nile tilapia growth: body size, temperature, dissolved oxygen, unionized ammonia and food availability. In the models, availability of natural foods was estimated by a relative feeding level parameter, which was a function of potential net primary productivity based on fish standing crop and limiting nutrients in ponds. The model for Nile tilapia in fertilized ponds was validated using growth data from 30 ponds, and successfully detected growth variations among ponds receiving the same nitrogen and phosphorus inputs. This model described 89% of the variance in growth in these ponds, and the relationship between predicted and observed growth rates had a slope of 1.02 and an intercept of -0.17, not significantly different from 1 and 0, respectively. This model indicated that the growth variations were caused by carbon limiting primary production during 55-99% of the culture period. Sensitivity analysis indicated that the parameters related to net energy from feeding were more sensitive than those related to fasting catabolism, and that the growth was most sensitive to food availability when DO was above its critical limit (1.0 mg/L), but was most sensitive to DO when it was below the critical limit. The model for both caged and open-pond Nile tilapia in the integrated culture system was validated using growth data from 28 ponds. The model described 95% and 83% of the variance in growth of caged and open-pond tilapia, respectively, in these ponds. Statistical analyses indicated there were agreements between predicted and observed values of both caged and open-pond tilapia. The model showed that the growth of open-pond tilapia was limited by phosphorus limiting primary production when total number of tilapia stocked in cages was not greater than 200 fish/pond, beyond which the limiting nutrient was phosphorus at the beginning of experiments and then shifted to nitrogen. The percentages of the culture period during which nitrogen limitation occurred increased from 0 to 84.4% with increases of artificial feed inputs. The model revealed nitrogen from biological nitrogen fixation accounted for 44.2-74.8% of total nitrogen available for primary production. Under the model assumptions, pelleted feed accounted only for 13.8 to 14.6% growth of open-pond tilapia when dissolved oxygen was above the critical limit (1.2 mg/L) for caged tilapia during entire experimental period, however, the percentages ranged from 19.0 to 51.0% when dissolved oxygen was below this critical limit. Sensitivity analysis showed that parameters for caged tilapia affected growth of open-pond tilapia but not the reverse, and reduced water quality (low dissolved oxygen and high unionized ammonia) further reduced growth of caged tilapia, but increased growth of open-pond tilapia. This study has successfully demonstrated the practicality of the tilapia-tilapia cage-cum-pond integrated rotation culture system based on intensive culture of adult Nile tilapia in cages and semi- intensive culture of small Nile tilapia in surrounding open water in earthen ponds. This approach is not only to augment the total aquaculture production, but also environmentally friendly Economic analyses also indicate that this system is feasible economically. It is an ideal Nile tilapia culture system for small- scale farmers. |
| Year | 1997 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AS-97-02 |
| 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 | Agricultural and Aquatic Systems(AS) |
| Chairperson(s) | Chang, Kwei Lin; |
| Examination Committee(s) | Edwards, Peter;Yakupitiyage, Amararatne;Chongrak Polparsert;Diana, James S.; |
| Scholarship Donor(s) | CRSP, Pond Dynamics/Aquaculture;United States Agency for International Development; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1997 |