A mass balance was constructed for nutrient flow through intensive marine shrimp ponds in which budgets for nitrogen and phosphorus were determined for a series of ponds in southern Thailand over two or three culture cycles. Ninety-five per cent of the nitrogen and 71% of the phosphorus applied to the ponds was in the form of feed and fertilizers. Of the feed input (at a food conversion ratio of 2) only 24% of the nitrogen and 13% of the phosphorus was incorporated into the shrimp harvested, whilst the remainder was retained in the pond and ultimately exported to the surrounding environment. The effluent water contained 35% of the nitrogen and 10% of the phosphorus discharged. Of the N and P exported in this effluent, 63-67% occurred during routine water exchange and the remainder during drainage on harvest. A major portion of the nitrogen (31%) and most of the phosphorus (84%) was retained in the sediments, emphasizing the importance of the correct removal and disposal of sediments between crops. Pond age (between two and six production cycles) did not markedly affect nutrient flows, whilst increasing stocking density increased the quantity of nutrients, but not their relative proportions.The results derived from the nutrient budget provide data which may help define effective management techniques for reducing potentially harmful nutrient levels within intensive shrimp ponds, and for reducing the discharge of nutrients to the local environment. The data may also assist in determining the carrying capacity of an area for shrimp farming, and the potential impact of its development on the environment.

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Abstract. A study was conducted to obtain a measure of the potency of some potential and commercially used feeding attractants for Penaeus monodon Fabricius. Behavioural trials monitoring the feeding response of the shrimp were used to gauge the attractant qualities of the substances. A growth trial recording the feed intake, feed assimilation, growth, food conversion and survival rates of the shrimp was used to assess further the feeding stimulant properties of the substances. Replicate groups of juvenile shrimp were fed semi‐purified diets containing 1·5% by weight of a range of potential feeding attractants. In the behavioural trial, diets containing taurine and a yeast extract were found to be significantly preferred to the control and all other diets. However, none of the substances appeared to act as potent feeding stimulants, producing statistically similar feed intake and assimilation rates to the control diet. However, taurine and an amino acid mixture designed to mimic a clam extract promoted the best performance of the attractants tested in terms of growth rate and feeding efficiency. Overall, the behavioural response of the shrimp to the feeding attractants was found to show similarities to the effects of attractant supplementation of feed on subsequent ongrowing performance, but not significantly so.