Effects of bamboo substrate and supplemental feeding on growth and production of hybrid red tilapia fingerlings (Oreochromis mossambicus x Oreochromis niloticus)

Periphyton growing on artificial substrates can increase the production of herbivorous fish in aquaculture ponds. Periphyton may be an alternative or a complement for supplemental feed in fingerling production. Growth and production of hybrid red tilapia (Oreochromis mossambicus x Oreochromis niloticus) were evaluated in twelve 5 x 5 x 1-m(3) concrete mud-bottomed tanks with bamboo poles for periphyton production. Submerged tank wall surface was 16 m(2). There were three densities of 1.5-m bamboo poles: 0, 98 and 196 poles/25 m(2), resulting in 0, 18.5 and 37 m(2) of additional pole surface per tank. Tanks were stocked with red tilapia try (average weight 1.2 g) at 25 fish tank(-1). At each substrate density, half of the tanks were fed with a fishmeal-based 35% protein diet at 5% body weight day(-1). Fish were harvested after 75 days. During the experiment, periphyton density on the substrates (ash-free dry matter [AFDM], ash and chlorophyll a) and water quality were monitored regularly. Water quality was favourable for fish growth and there were only minor differences between the treatments. Periphyton biomass density on the substrates initially increased and was subsequently reduced during the experiment due to fish gazing. Final mean (+/-S.E.) gross fish yields (g/25 m(2)) without substrates were 850.3 g (+/-73.7) without and 1225.7 (+/-193.7) with feeding. With 98 poles tank(-1), gross yields increased to 1803.8 (+/-79. 1) without and 2141.8 (+/-221.7) with feeding. With 196 poles tank(-1), yields were not or only marginally higher. Although more experiments are needed to optimize periphyton density in relation to fish size and stocking density, the results show that periphyton can replace or complement supplemental feeding in tilapia fingerling culture. (C) 2004 Elsevier B.V. All rights reserved.