Marine Recirculating Systems In Israel-Performance, Production Cost Analysis And Rationale For Desert Conditions

Abstract

A semi-commercial 100 m3 marine recirculating system (RAS) was designed, based on the results of a 5 m3 experimental system. The system was stocked with gilthead seabream (Sparus aurata). After 200 days, the fish in the semi-commercial system had a similar weight (about 330 g) and density (78 kg/m3) and identical survival (99%) and FCR (1.8) as similar fish grown in a flow-through system (FAS). Annual production in the RAS was calculated as 90 kg/m3. Seawater consumption was 3.5-4 m3 per kg fish produced, resulting in an average water exchange rate of 80% of the system volume per day. While this is relatively high compared to freshwater RAS, the marine RAS required only 10% of the sea water consumed in an FAS. Since sea water is an inexpensive input, water consumption was a minor component of the total production costs in the RAS (approximately 6%). The economical analysis for a theoretical 500 ton/y farm showed that the main capital investment components would be the rearing volume (fish tanks) and the biofiltration unit, representing over 60% of the total investment. The highest production costs would be feed, fingerlings and return on the investment, in that order, representing over 50% of the production costs. CO2 stripping may limit further intensification because the limited surface area of the tank limits the number of paddlewheels that can be used. Also, the DO/TAN ratio may be a factor limiting achievement of a higher nitrification rate and reduction of the biofilter size. Based on the results of this study, a 100 ton/y pilot plant is currently being designed as a model farm.