Mathematical principles of production management and robust layout design: Part I. 250-ton/year recirculating aquaculture system (RAS)

This study describes the design and management of an effective recirculating aquaculture system (RAS). The RAS design involves many aspects, both physical and biological: (1) a desired turnover, (2) fingerling arrival frequency, (3) number of fingerlings per batch, (4) number of days in a growth phase, (4) timing of grading and sorting, based on (5) fish growth rate, and (6) number of culture tanks. The design criteria were: (1) turnover of 250ton/year, (2) fingerling arrival frequency of 12batches/year, (3) biomass density ≤60kg/m ³, (4) two fish batch-sorting and batch-splitting events, and (5) a robust design to accommodate two species-slower- and faster-growing species. The culture tank was regarded as a queuing system in which neither a " queue" (overholding of fish) nor an idle culture tank is allowed, enabling modeling of the fish farm as a queuing network. A queuing model, stochastic simulation, optimization, and six sigma robust design were developed, validated, and implemented.The optimal layout was found to comprise three growth phases, with 1, 8, and 24 culture tanks, respectively. Optimal parameters included: arrival frequency-a single fish batch into the system every 30 days; then 30, 120 and 180 days in the 1st, 2nd and 3rd phases, to 42, 200, and 440g, respectively. The optimal values satisfied the criteria of biomass density below 60kg/m ³ and culture tank utilization above 93%. Expected production was 250-276ton/year. The proposed layout can accommodate different fish species with different growth rates under the same proposed layout, culture volume, density, and schedule. The numerical values reflect local aquatic conditions, but the proposed methodology can be applied elsewhere.