Recirculating Aquaculture Systems (RAS) offer significant advantages over open aquaculture systems. These advantages are heavily underutilized because the application of RAS is limited. Growth retardation is the major restraint and until this is eliminated, economic feasibility of aquaculture in RAS remains marginal, significant aquaculture production in RAS will not be established and the advantages of RAS remain under utilized. Growth retardation has been observed for most species cultured in RAS but the causes remain obscure.
The turbot industry is the first aquaculture industry that applies RAS on a large scale to produce market size marine fish. Therefore the turbot industry is the first aquaculture industry to be heavily affected by growth retardation. Growth of turbot in RAS is 15-20% lower compared to flow through systems. Individual turbot farms have tried but were unable to solve the problem by them selves Therefore they need to join forces with other turbot farms and RTDs in this project. Without the elimination of growth retardation it is either back to flow through systems or an insecure and marginally feasible future with RAS.
The working hypothesis for this project is that growth retardation is caused by accumulation of growth inhibiting factors (GIF) in the culture water. Both the fish and bacteria are believed to produce these GIF.