Utilization of Periphytic Natural Food as Partial Replacement of Commercial Food in Organic Tilapia Culture - An Overview

Abstract

ABSTRACT This article summarizes the results obtained during five years of research at the Dor Fish and Aquaculture Research Station on partial replacement of commercial food by periphytic natural food in the culture of organic tilapia (hybrid Oreochromis aureus (Steindachner) x Oreochromis niloticus (L.)). Tilapia culture experiments were conducted in earth ponds with and without substrates, utilizing different substrates. Tilapias of sizes ranging from nursery to market-size fish were tested. Fish were stocked at densities common in organic fish culture, i.e. 5 tilapia/m2 at the nursery stage, 1.2-1.4 tilapia/m2 at the grow-out stage. Substrate experiments were carried out in 1 m3 cages protected from fish grazing to test growth of periphyton on materials with different characteristics. The findings show that the inclusion of substrates in the water body at an amount equivalent to 40-50% of the pond water surface, allows the reduction of commercial food input by 30-40% without significantly hampering fish growth rate. It is recommended to use rough, rigid, white substrates, on which periphyton growth of 2 g dry matter/m2/day has been measured. A figure and a table are provided as a tool to estimate periphyton contribution to the fish food ration, enabling the adjustment of the remaining daily food portion to be supplied as fish biomass increases during the culture period. Applying this technology will save food and money in the culture of organic tilapia, and it can also be appropriate in the conventional pond culture of tilapia as a method to reduce feed costs and increase sustainability.