The survival and growth rates of both shrimps and tilapia were quite good in the first two months. As it common in a traditional extensive system, the farmer did not feed the shrimps for the first month and relied on the natural feed. After a heavy rain, which was not common in May/June, the water quality was low.
At 56 days into the culture, fifty shrimps were found dead with some lesions: broken pleopod, some black spots on the body, and red muscle. Vitamin C (one tablet each feeding) and coconut oil were added into the feed to treat the diseases. Fifty kilogram of lime was also added into the pond. Samples of dead shrimps were sent to Ujung Batee Brackish Aquaculture research Center for analysis. PCR confirmed that the shrimps experienced WSSV. After three days, another 200 dead shrimps were found, and the farmer decided to conduct a sudden harvest. Other than the dead shrimps, it was noticed that the water color changed from yellow to brownish-red at 40 days, and again changed to yellow two weeks before the sudden harvest.
All the tilapia survived in the reservoir up to the time of harvest (after six months). The finding suggests that the tilapia was able to survive in reservoir and maintained good growth rate. Even though other findings in lab scale or field observation suggest that the tilapia has the ability to minimize the risks of Vibriosis and WSSV, the exact mechanism and under what condition are remain unclear. Another question is whether the tilapia has direct inhibition against both pathogens or indirect inhibition by stimulating microbes or microalgae to grow. Further research needs to be conducted to investigate the mechanism.
The field experiment in Indonesia was funded by the L’Oréal Indonesia For Women in Science Program. SN would like to thank the US Department of State, the Schlumberger Foundation Faculty for the Future Program, and the University of Arizona for supporting the PhD study and research component in the US.
Huervana. F.R., J.J.Y De la Cruz, C.M.A.Caipang. 2006. Inhibition of luminous Vibrio harveyi by green water obtained from tank culture of tilapia Oreochromis mossambicus. Acta ichthyologica et piscatorial 36 (1): 17-23
Tendencia, E.A. M.R. de la Pena. C.H. Choresca. 2006. Effect of shrimp biomass and feeding on the anti-Vibrio harveyi activity of Tilapia sp. in a simulated shrimp tilapia polyculture system. Aquaculture 253 (1-4): 154-162.
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