Pangasius production in Vietnam is not always done sustainably. The wastewater from the fishponds, which produce large quantities of faecal waste, is locally creating environmental problems in the Mekong River.
Wageningen Aquaculture, together with Dutch and foreign partners, is searching for solutions. Researchers are looking at whether it is possible to change the feed composition and how the ponds are set up.
Pangasius production in Vietnam has grown dramatically in the last fifteen years. In 2002 the country produced about one hundred thousand tons a year, now the figure stands at 1.3 million tons. This is in the same league as the worldwide salmon production. However, pangasius production is concentrated in one part of the Mekong Delta and, apart from being an important income source, this is also a source of concern: the ponds produce large amounts of faecal waste which is discharged into the Mekong River.
The excrement not only creates problems outside but also inside the ponds. It is responsible for bad water quality – low oxygen content, high ammonia levels – and this in turn weakens the condition of the fish, the researchers working on this project believe. The problem has been instigated by the feed used. It is low in fat and nutrients and high on plant-based carbohydrates and fibre, as a result of which the fish excrete tiny organic particles that cloud the water.
The primary focus of research is therefore improvement of the feed composition. The hope is that it is possible to make feed richer in nutrients and fat, and poorer in fibre and carbohydrates, so that the fish excrete l more compact particles which are easier to remove from the water. The second focus is on pond design. The researchers think that the organic content of the water can be improved by using elements from recirculation systems. One idea is to divide ponds up into a part where the fish live and a part where more compact faeces can settle on the bottom of the pond. Instead of this sludge being discharged into the Mekong River, pangasius farmers will be able to sell it to crop farmers.