BIO-ENERGETIC MODELING OF GROWTH AND WASTE PRODUCTION OF NILE TILAPIA
(OREOCHROMIS NILOTICUS L.) IN RECIRCULATION SYSTEMS.
Dr. M.C.J. Verdegem and Dr. Ir. A.A. van Dam.
Fish Culture and Fisheries Group, Department of Animal Sciences, Wageningen University.
P.O.Box 338, 6700 AH Wageningen, The Netherlands.
A bio-energetic fish growth simulator (FGS) model was developed for Clarias gariepinus
(Machiels 1987) and subsequently adjusted for the culture of Oreochromis niloticus,
Oncorhynchus mykiss (van Dam 1995) and Colossoma macropomum (van der Meer 1997).
The FGS model was extended with a fish waste module (FWM), to calculate the total waste
production due to feeding by tilapias grown in indoor recirculation systems. Wastes
calculated included the amount of uneaten feed, feces, and CO2 and NH4+ production. The
amounts of wastes produced were also expressed as chemical oxygen demand (COD) (Nijhof
1994). The model was calibrated and validated using two independent data sets, made up
each of 30-40 aquarium experiments, monitoring growth and changes in proximate body
composition of O. niloticus between stocking and harvesting. Fishes belonged to 3 different
weight classes (10-50, 40-140 and 60-210 g), feeding levels ranged between 5 and 30 g kg-0.8
d-1, and 39 and 52 % protein commercial pellets were fed. The principal read-out parameters
for calibration and validation of the model were protein and fat deposition. Because waste
production is the result of the same metabolic processes that lead to protein and fat
deposition, it was assumed that waste production was simulated well when protein and fat
deposition are. The calibrated model was used to review the effect of feeding level and
dietary protein level on waste production per kg dry matter or kg protein fed, and per kg
tilapia biomass produced. Finally, tilapias were grown in 3 separate recirculation systems,
quantifying nutrient input and the amount of wastes recovered from each system. The latter
was defined as the sum of waste discharge (sludge and sludge water drained) and within
system accumulation of wastes (organic and inorganic nutrients) during culture. Possible
causes for the observed differences between the amount of wastes recovered and the
simulated amount of waste produced are discussed.
Machiels M.A.M..“ A dynamic simulation model for growth of the African catfish, Clarias gariepinus
(Burchell 1822)”. Ph.D. thesis, Wageningen Agricultural University, Wageningen, The Netherlands,
110 pp. 1985.
Nijhof M.. “Theoretical effects of feed composition, feed conversion and feed spillage on waste discharges in
fish culture”. Journal of Applied Ichthyology, 10, 274-283. 1994.
Van Dam A.A.. “Modeling studies of fish production in integrated agriculture-aquaculture systems” . Ph.D.
thesis, Wageningen Agricultural University, Wageningen, The Netherlands, 163 pp. 1995.
Van der Meer M.B.. “Feeds and feeding strategies for Colossoma macropomum (Cuvier 1818): fish growth as
related to dietary protein”. Ph.D. thesis, Wageningen Agricultural University, Wageningen, The
Netherlands, 137 pp. ISBN 90-5651-038-X. 1998.