Project Details

In combination with floating net cage production properties, a quantitative estimate is made concerning the nitrogen flux and its temporal variations per unit of fish biomass. The nitrogen flux is converted to discharges per farm volume for a given stocking density. The result is the overall emission which can be used in conjunction with water quality and deposition models for assessment of the impacts and estimation of carrying capacities of floating net cage cultures (Fig. 2). The mass balance model was initially developed to quantify the emissions due to groupers. Extensions to other fish species are currently underway. 

Figure 1AB diagrams

Figure 1: a) Computed vs. observed growth of Tiger grouper (Epinephelus fuscoguttatus) as cultured in Pegametan Bay, Bali, Indonesia. b) Feed records of Tiger grouper fed with trash fish as recorded during the grow out period of the cultured fish.

Figure 1CD diagrams

Figure 1:c) Resulting feed conversion ratios during the grow out period compared to common FCR of similar cultures. d) Nitrogen emissions per unit of fish biomass.

The mass balance model is integrated within the SYSMAR DSS. Much work was done to study the behaviour of farm wastes in the environment. Water quality models simulating the release and fate dissolved nitrogen from multiple farms indicated the importance of physical driving forces to efficiently accommodate farm waste and allow the environment to utilize its resilience capacity. A combination of hydrodynamic modelling and water quality modelling releasing the estimated nitrogen flux allowed the study of ammonium and nitrate through the fish farm region and how individual production capacities can be managed to minimize nutrient concentrations.

Research division

ECOLAB – Coastal Ecosystems


Dr. K.-J. Hesse
Research and Technolgy Centre Westcoast, University of Kiel (FTZ)


M.Sc.  S. van der Wulp (FTZ)