Modelling the growth of Nile Tilapia (Oreochromis niloticus) feeding on natural resources in enclosures in Laguna de Bay (Philippines)

Laguna de Bay (Philippines), one of the largest freshwater bodies in the Southeast Asia, is located near Metro Manila. The lake is an important resource for the local population because of fish production: fishing and aquaculture are relevant activities for the economy of the area. Nile Tilapia (Oreochromis niloticus) is one of the cultured species and it is grown within net cages in the lake. In this paper, a model is proposed to describe the growth of Nile Tilapia under natural conditions; food sources have been considered to be phytoplankton, zooplankton and suspended organic matter (detritus), without additional feed supply. The metabolic approach has been adopted to describe fish growth. The parameters characterising fish metabolism have been estimated for O. niloticus or similar species, according to literature information. The model has been applied to twelve growing conditions representative of increasing stocking densities and of different growing periods. Model results have been successfully compared with the experimental data reported in literature. This model has been used to estimate the amount of natural food (phytoplankton) exploited by the culture of O. niloticus with the final aim to quantitatively relate lake’s water quality with fish growth and production.