Added carbohydrates aid production in extensive shrimp culture

Adding a carbon source to intensive shrimp production systems can control total ammonia nitrogen (TAN) levels and improve feed conversion. Studies have shown that immobilization of inorganic nitrogen only occurs when the carbon:nitrogen (C:N) ratio of the organic matter is higher than 10. Immobilization of TAN results in the production of bacterial cells rich in single-cell protein that can be utilized as food by carp, tilapia, and shrimp. As a result, the feed-conversion ratio of the supplemental feed applied to ponds decreases, making it possible to use lower-cost, lowerprotein feeds. Although commonly applied in intensive aquaculture, the technique of C:N ratio control is not used in extensively managed ponds, even though these systems support much of the farmed shrimp production worldwide. The authors recently evaluated the effects on water quality and production of adding organic carbon to extensive stagnant shrimp ponds in India. Continuous mixing to keep dissolved and particulate matter dissolved in the water column is a key factor in the success of C:N ratio manipulation in intensive systems. The challenge, therefore, was to determine if the added carbohydrates would positively impact water quality before precipitating to the bottom.