Mathematical Modeling of Dissolved Oxygen in Fish Ponds

Document Type: Original Research Paper

Author

School of Environmental Science and Technology, Ardhi University (ARU), P.O. Box 35176, Dar es Salaam, Tanzania

Abstract

A mathematical model was developed to predict the effects of wind speed, light, pH, Temperature,
dissolved carbon dioxide and chemical oxygen demand (COD) on Dissolved Oxygen (DO) in fish ponds. The
effects of organic feeds, aeration and fish activity were added to the model developed by Kayombo et al. for
Waste Stabilization Ponds (Ecological Modeling 127(2000): 21-31) to reflect the situation in fish ponds.
Model calibration and validation was done by use of average DO, pH, temperature, COD, CO2 and algae
biomass data measured from RETCO fish ponds in Dar es Salaam; and light intensity data were adopted from
Kayombo et al. (2000). Model results showed a linear relationship between simulated DO and measured DO
in fish pond (r2 = 0. 87) for model calibration and (r2= 0.88) for model validation. Simulation results also
showed a general decrease of DO with time in 13 days by 28% and 38% for first and second batch, respectively.
Thus, the model developed in this study could be used to predict the DO dynamics in fish ponds. Based on the
model results, successful cultivation of healthy fish may require that retention time for water in the fish pond
be 10 days.

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