The Israeli Journal of Aquaculture - Bamidgeh 55(4), 2003, 243-257

FIELD REPORT: MARINE RECIRCULATING SYSTEMS IN ISRAEL - PERFORMANCE, PRODUCTION COST ANALYSIS AND RATIONALE FOR DESERT CONDITIONS


Noam Mozes*, Micha Eshchar, Daniel Conijeski, Michael Fediuk, Arik Ashkenazy
Israel Oceanographic and Limnological Research, The National Center for Mariculture, P.O. Box 1212, Eilat, 88112, Israel

Fernando Milanez
ARDAG Ltd., Eilat, Israel

(Received 1.10.03, Accepted 30.11.03)

Key words: cost analysis, mariculture, production, recirculating systems


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 (Sparusaurata). 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.


*Corresponding author: mozes@ocean.org.il

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