The role of fish culture in the provision of fish for food is examined with special reference to Western Europe. The use of recirculating systems for intensive fish culture is considered and the need for establishing their feasibility for commercial culture recognised. The lack of suitable guidelines for the design and operation of such systems is seen as a major limitation. A research programme was initiated, resulting in the development of a simulation model.
Firstly a number of recirculating systems were designed,constructed and commissioned and their behaviour and performance monitored. Three areas for further investigation were noted and experiments to consider growth and food conversion, the production and accumulation of wastes and filter performance were conducted. Based on the understanding gained a simulation model was constructed. The model was verified using graph theory, by inspection of standard runs for maximum, minimum, mean and variation and by sensitivity analysis. The model was validated by the comparison of model output with the actual behaviour of the system using a range of stocking densities and ration levels. To improve agreement between predicted and measured diurnal variations in water quality, modifications to the simulation of ammonia production and short-circuiting in the filter were considered.
The use of the model is considered; to indicate areas of inadequate knowledge, to improve understanding of the behaviour of the laboratory systems and to develop guidelines for determining carrying capacity and optimum design of filters for recirculating systems. Use of the model for predictive purposes posed a number of difficulties, and it is concluded that the main value of the model is as an educational tool
