EFFICIENCY OF WATER-USE OF AN INTEGRATED FISH VEGETABLE COCULTURE SYSTEM/

Fish and vegetable production were linked in a recirculating water sys tem designed to achieve a high degree of efficiency of water use for f ood production in addition to functional and technological simplicity. Hybrid tilapia Oreochromis mossambicus x O. niloticus L. were grown i n tanks associated with biofilters (sand beds) in which tomatoes Lycop ersicon esculentum were grown. The effect of four biofilter volume (BF V)/fish rearing tank volume ratios (0.67/1, 1.00/1, 1.50/1, 2.25/1) on water use efficiency was evaluated. 'Laura' (first experiment) or 'Ke walo' tomatoes were grown 4/m(2) in biofilters of four different sizes and surface-irrigated 8 times daily with water from the associated fi sh tanks. Daily water consumption increased with BFV/tank ratios and w ith time. Fish production rates increased with biofilter volume in the first experiment, but were not significantly different in the second experiment. Total tomato fruit yield per plot increased from 13.7 to 3 1.7 kg (Experiment 1) and from 19.9 to 33.1 kg (Experiment 2) with inc reasing BFV/tank ratio. For fish plus fruit, total energy production i ncreased from 4,950 to 8,963 kcal/plot and from 4,804 to 7,424 kcal/pl ot in Experiments 1 and 2, respectively, and protein production increa sed from 536 to 794 and from 352 to 483 g/plot in Experiments 1 and 2, respectively, with increasing BFV/tank ratio. Trends in water use eff iciency for production of food energy (kcal/L) and of protein (gn) in tomatoes and fish were complex. Water use efficiency for total energy production (fish plus fruit) did not significantly differ with biofilt er volume. Economy of water use for total protein production (fish plu s fruit) decreased significantly with increasing BFV/tank ratio. The c omponent ratios of the system may be manipulated to favor fish or vege table production according to local market trends or dietary needs, an d thus may have economic potential in areas of limited water supply an d high demand for quality food.