Pangasius

Pangasius farmers continually seek to improve the efficiency of feeding methods in order to reduce operational costs and to minimise waste feed settling on the bottom of the pond. Waste feed, along with other organic discharges from farming operations, can potentially lead to pollution of receiving waters and adversely affect aquatic life through de-oxygenation and algal blooms, which can be associated with nutrient increase. The key nutrients likely to cause problems for receiving waters are nitrogen and phosphorus¹.

The type and quality of feed used will affect the discharge of nutrients. To improve their performance, farms should monitor feed utilisation efficiency, the quality of the pond effluents and water quality in the receiving water body. Monitoring methods are documented within certification standards.

Farms should also document and record how they dispose of pond sludge and any other solid wastes. Pond sludge and waste water is used to fertilise agricultural land surrounding pangasius farms in areas such as the Mekong Delta^{2, 3}. Sludge repositories are often used on pangasius farms and are required by many certification schemes. The use of sedimentation basins or dedicated ponds to capture particulates in waste water is effective but more work is required to remove dissolved nutrients³. One area of growing interest is the use of clean-up technologies such as constructed wetlands, where aquatic plants such as water hyacinth can help trap fine suspended particles and utilise dissolved nutrients⁴. These plants can then be harvested giving a farmer an additional crop and alternative income stream.

Recirculation of water within an aquaculture facility is often cited as a sustainable means of reducing environmental impacts from waste water discharges, as well as reducing escapees and helping diseases control. Investment costs to enable recirculation are significant. Pangasius farmers are unlikely to consider this technology unless, for example, they are located in areas of salt water intrusion and need to limit saline water entering their ponds, and the price for the fish they produce can be increased⁵.