MARINE AQUACULTURE EFFLUENT MONITORING - METHODOLOGICAL APPROACH TO THE EVALUATION OF NITROGEN AND PHOSPHORUS EXCRETION BY FISH

A wide range of methodologies is used for measurement of excretion by fish and for the evaluation of dissolved nutrient loadings from fish farms. In order to improve the accuracy and utility of monitoring devices, two specific apparatus have been adapted and improved: continuous sampling for simultaneous analysis and pooled samples continuous collection for later analysis. Provided that pooled samples are stabilized with 10 ml litre(-1) chloroform at ambient temperature after phytoplankton and organic matter removal, these methods give similar and accurate results when applied to nitrogen-dissolved compounds, and are applicable to nutritional studies. Applied to soluble phosphate, the pooled method gives, after 72 h storage, results within 5% of the exact value. It is suitable for statistical evaluation of nutrient loadings on large-scale field studies.