Evaluation of organic tilapia culture in periphyton-based ponds

Abstract

The introduction of hard surfaces in the water column to induce the growth of biofilms and peri- phyton on these surfaces is a method used to increase natural productivity of the water body and food for cultured aquatic organisms. In periphyton-based systems in Africa and Asia, substrate introduction and consequent periphyton development positively affected water quality and pro- duction of the target species. In Israel, this technology is being evaluated in the culture of organ- ically produced tilapia. Among other restrictions imposed by organic standards, fish stocking densities must be low and only organic feeds and manures must be supplied. Organic pelleted feeds cost twice as much as regular aquaculture feeds. Since feed constitutes the major pro- duction expense, economic viability is hampered by using costly organic feeds. An experiment was performed at the Dor Aquaculture Station to explore methods of improving natural food pro- duction for tilapia and reducing added feeds. Submerged plastic surfaces equivalent to 40% of the pond surface area were immersed in polyculture ponds containing 85% hybrid tilapia (Oreochromis niloticus x O. aureus), together with a reduction of 40% of the amount of pelleted feed. The treatment improved nitrification and saved 40% of the feed costs, with only a 10% reduction in the tilapia growth rate and yield. These results indicate that periphyton-based aqua- culture is an appropriate technology for reducing production costs and allowing economically viable organic tilapia production.