LARGE SCALE HIGH-RATE BIOFLOC TANK CULTURE OF TILAPIA IN MALAWI: FROM INCEPTION TO TECHNICAL SUCCESS.

In 2006 SustAqua Fish Farms (Pty) Ltd was commissioned by Chambo Fisheries to design a large-scale Biofloc Technology (BFT) fish farm on the outskirts of Blantyre, Malawi based upon the use of feral tilapia species Oreochromis mossambicus and Oreochromis shiranus. It was only in September 2013 that the project infrastructure was ready to support production in four of eight 766m³ sequentially managed continuous BFT grow-out tanks of a proprietary design.

Following the implementation of bioenergetic feeding rate models average feed conversion ratio's of 1 : 1 on 20.2% protein feed (providing a C: N ratio of approximately 15.5:1) where routinely achieved under large scale culture conditions. The calculated contribution of filter feeding on biofloc by O. mossambicus and O. shiranus falls in the range of 20-25% of daily Digestible Energy (DE) requirements for fish in the size range 20-220g. Net Protein Retention (NPR) and Net Energy Retention (NER) values were greater than 75% and 40% respectively significantly higher than a typical commercial Recirculated Aquaculture System (RAS), lake cage culture and greenwater pond farming operations. These results would suggest that properly designed and managed biofloc tank culture of tilapias is potentially the most efficient form of feedlot livestock production outperforming lamb, broiler chickens, pigs and beef steers as well as Atlantic salmon in net-pens and tilapia under typical lake cage culture, greenwater pond farming and RAS conditions in terms of protein recovery on an edible meat yield basis.

These results, notably significant feed cost savings, high annual production yields (attributed to the use of a sequential production schedule) coupled with the efficient use of power and capital employed, year-round production potential (under greenhouse enclosures where necessary) and good fish flavour quality offers an interesting new dimension for tilapia aquaculture development on the periphery of major African cities on the continent.