INTEGRATED TANK CULTIVATION OF SALMONIDS AND GRACILARIA-CHILENSIS (GRACILARIALES, RHODOPHYTA)

Oncorhynchus kisutch, O. mykiss and Gracilaria chilensis cultivation i n intensive tank systems is feasible. The environmental benefits assoc iated with the development of integrated tank cultivation were establi shed by analyzing previously published and unpublished data on fish pr oduction and food conversion efficiency, particle discharges in fish e ffluents, as well as biomass production, nutrient uptake effiency data of Gracilaria, with special emphasis on ammonium. The results indicat e that fish production can reach 30 kg m(-3) during a production cycle , and food conversion can be maintained stably at 1.4 g food g fish(-1 ) production during the entire cultivation period. The solid particle discharges can be as high as 2.1 g (dry) kg fish(-1) day(-1) during th e spring and summer, when salmon cultivation reaches its highest densi ties. The nutrient that increases most in fish effluents is ammonium, reaching concentrations as high as 500 mu g l(-1), also in spring and summer. Gracilaria production can reach production rates as high as 48 .9 kg m(-2) year(-1) and is able to remove 50% of the dissolved ammoni um in winter, increasing to 90-95% in spring. These results are integr ated into an income-analysis model, adding the extra income for Gracil aria harvesting and internalizing the environmental benefits for a 100 -ton salmon production unit, which indicates that an additional total revenue of over US$ 60000, representing around 10% of the total income , is possible.