Problems and issues of Nile tilapia cage farming in Taal Lake, Philippines
2000
Yambot, A.V. (Central Luzon State Univ., Nueva Ecija (Philippines). Coll. of Fisheries-Freshwater Aquaculture Center)
An assessment of the different problems and issues of cage farming Nile tilapia, Oreochromis niloticus, in Taal Lake was conducted. Selected but important water quality parameters were identified and monitored. Ammonia was found to be extremely high while dissolved oxygen was very low. Observed parameters were indications of high nitrogen loading in the cage site. Some identified problems that cause the pollution of Taal Lake were high stocking density, high feeding rates, chessboard-type positioning and congestion of fish cages, floating dead fish from mass mortality abounding in the area, and scattered waste materials. These various conditions are considered stressors that predispose the fish to chronic diseases. Instances of fish kill were also observed under acute conditions. High mortality was commonly observed during summer when there is no wind to circulate the water. Prolonged and sudden rush of wind during summer has been suspected to overturn the lake bringing up to surface noxious and anoxic water to where the cages are positioned. Reduction in the stocking density, single-line positioning of cages, installation of improvised aerator during problem situations leading to disease outbreaks and high fish mortality, waste disposal management, and continuous monitoring of limnological parameters were some recommendations made to improve the condition of the lake. Reduction in the stocking density and single line positioning of cages will distribute wastes thinly from cages and allow circulation of water. Government role to mitigate the problems is also emphasized.
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