NITROGENOUS AND PHOSPHORUS WASTE PRODUCTION IN A FLOW-THROUGH LAND-BASED FARM OF EUROPEAN SEA-BASS (DICENTRARCHUS-LABRAX)

A study on nitrogenous and phosphorous waste production in European se abass (Dicentrarchus labrax) was carried out in a flow-through land-ba sed farm. The main objectives were (i) to calculate nitrogenous (N) an d phosphorous (P) waste production (particulate and dissolved) from in situ measurements for different rearing ponds with specific fish biom asses, fish sizes and flow rates, (ii) to establish nitrogenous and ph osphorous waste production budgets, ratios and equations, and (iii) to compare, for the whole farm, in situ measurements to estimate N and P waste production from waste equations. Waste production was manifest by an increase in concentrations of total ammonia nitrogen, total Kjel dhal nitrogen, particulate nitrogen, dissolved phosphorus and total ph osphorus concentrations in the outlet water compared to the inlet wate r for both batches and whole farm. However, no production of nitrite o r nitrate was observed. In our budgets, the N and P amounts from bioma ss gains and wastes were explained by the N and P derived from feed ov er the range 83.9-105.2 % and 66.5-104.6 % respectively, depending on the fish batch. Values were respectively 103.4 and 87.5 % for the same calculations in the farm. When the whole-farm waste production was ca lculated from previous equations derived from batches, and then compar ed with the measured data, the percentages of recovery (estimated by t he ratio predicted data/measured data) were 88 and 94 % for total-N an d total-P respectively. (C) Ifremer/Elsevier, Paris.