Evaluation of water productivity and fish yield in sewage-fed vis-à-vis fertilized based carp culture

Reuse of wastewater in aquaculture provides a scope to enhance water productivity of the system. Quantification of nutrient inputs incorporated through treated domestic sewage with varying dosages viz. 79.3 × 105 l ha−1 and 67.7 × 105 l ha−1 and water productivity in a controlled carp culture system were assessed in comparison to those involved in a fertilized based one, with a view to correlate among physical, chemical and biological processes involved in fish yield under the systems. The net water productivities were measured on the basis of net return values (in Indian rupees; INR) from the carp production systems at a stocking density @ 5000 per ha with four species combination. Selected relevant water parameters such as dissolved oxygen, total alkalinity, biochemical oxygen demand (BOD5) in sewage effluent and fertilizer based systems were monitored along with certain biological parameters viz. gross primary productivity, fish production and water productivity. The nutrient inputs in terms of total ammonia–nitrogen (TAN) in effluents, total nitrogen (TN) in fertilizers and phosphorus (P2O5) in both effluents and fertilizers were found significantly correlated with biological production. The results of the experiment revealed that the sewage incorporation at 79.3 × 105 l ha−1 yielded similar gross fish production as recorded from fertilizer based system, whereas net water productivity using sewage as nutrient source was found 64% higher than that of a fertilizer based system.