Trend of physico-chemical parameters in relation to the aquaculture establishment at a tropical lake in Malaysia

A study was conducted to evaluate the impacts of the tilapia cage culture located within 100ha of the Aquaculture Industrial Zone (AIZ) on the water quality of Temengor Reservoir. Sampling on the physico-chemical parameters was conducted at 15 sampling points at depths of 0m, Secchi depth, 5m, 10m, and 15m. The values of these parameters were observed to be dependent on the distance from the fish cages; the trend of water quality parameters deteriorated upon approaching the fish cages. The higher concentration of nutrients was attributed to the nutrient leaching from uneaten food pellets, fish excretion, and decomposition of nitrogenous and phosphate compounds. Besides, the chemical substances such as vitamins and antibiotics used to increase aquaculture production might also contribute to loads of nutrients. However, the concentrations of nutrients and chlorophyll-a at Temengor Reservoir were still within the acceptable limit of environmental health. The detrimental effects of the fish cages might be reduced by the dilution factors based on volume, depth, and water level of the reservoir and rainfall, resulting in low concentrations of nutrients on the surface compared to other previous studies conducted in rivers, streams, and shallower lakes.