Consumption of periphyton and bioseston by Mozambique tilapia in aqua dams with three different substrates

Abstract

Periphyton-based aquaculture can reduce feed input costs. Here we characterised the periphyton and bioseston formation in aqua dams stocked with net, plastic, and stone substrates. The consumption of periphyton and bioseston from the net substrate by Mozambique tilapia Oreochromis mossambicus fingerlings was evaluated. Three experiments were conducted. In the first experiment, net, stone, and plastic were deployed in triplicates in aqua dams. The net substrate registered the highest (7.74 ± 1.45 g m-2, ±SE) periphyton biomass. Network analysis showed connectedness between the substrates. The degree centrality showed that the net substrate had the highest score, indicating that there were more groups of species with similar functions growing on the net substrate. The net substrate was subsequently used in the second experiment to determine the consumption of periphyton and bioseston by tilapia fingerlings in aqua dams. Three treatments were assigned: N100 (fish fed 100% commercial diet); N50 (fish fed 50% commercial diet); and N33 (fish fed 33% commercial diet). Growth performance did not differ significantly among the treatments, although N50 showed a trend for a higher growth. This suggests that periphyton may be capable of nutritionally compensating for the partial withdrawal of commercial feed. A third experiment was conducted in fibreglass tanks to determine the preference of tilapia between periphyton and bioseston. The prominent values showed that tilapia preferred to feed on bioseston. The best growth performance was achieved in a periphyton-based aquaculture system, and deployment of the net substrate is recommended in tilapia ponds.