Systems engineering for ornamental fish production in a recirculating aquaculture system

The aim was to develop a simulation model for determining the optimal layout and management regime for ornamental fish recirculating aquaculture system (ORAS). The work plan involved: (1) quantifying the effects of fish growth rates, the nature of the products, and the management practices; (2) developing a mathematical simulation model of the ORAS, taking into account all factors that directly influence system profitability; and (3) maximizing the production level attainable with the existing facilities and within the prevailing costs, thus raising the profitability of the ORAS. The resulting model is process-oriented; it follows the flow of fish through the ORAS facility and generates an animated graphic representation of the processes through which the fish pass as they progress through the system. The model enables a user to anticipate how system profitability would be affected by changes in: design, operating practices, costs of inputs, and/or prices of products. A step-by-step approach was taken in designing an optimal RAS that both met marketing demand and conformed with stocking-density limits. Optimal design specifications were presented for several case studies based on data from an ORAS in Kibbutz Hazorea, Israel where koi (Cyprinus carpio) are raised in a recirculating system. The addition of one reproduction cycle per year reduced the maximum biomass load from 8 to 5 ton. The addition of two reproductions per year would enable the system to process an additional 1 million fingerlings per year, elevating sales by 60% without changing the biomass load. If the waste rate could be reduced from 80 to 44% while processing the same number of fingerlings, sales could be increased by a factor of 3 without exceeding the biofilter limits. If the final koi size were to be reduced from 50 to 25 cm, the number of fingerlings could be doubled (to 5 million) while maintaining the existing low biomass load. Alternatively, purchasing larger fingerlings (4.5 instead of 0.1 g) might cause the biomass load to exceed the filter limitation (14 compared with 7.4 ton). Further research should include more extensive testing and validation of the integrated model, which then could be disseminated within the aquacultural community.