The effects of artificial substrates on freshwater pond productivity and water quality and the implications for periphyton-based aquaculture

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As a first step in assessing the viability of periphyton-based fish production in South Asian pond aquaculture systems, the effects of artificial substrates on development of periphyton and on water quality were evaluated. Earthen ponds (10 × 7.5 m) were provided with an artificial substrate constructed from poles of either bamboo, kanchi or hizol tree branches (1.0 m 2 artificial substrate per m 2 pond surface). Higher periphyton biomass, in terms of dry matter (DM) (4.9 mg cm –2) and chlorophyll a (11.5 μg cm –2) developed on hizol and bamboo, respectively. Periphyton ash content was higher on hizol (41%) than on the other two substrate types (29%). Protein content of the periphyton growing on bamboo (38% of ash-free dry matter (AFDM)) was 50% higher than that on the other two substrate types. Maximum periphyton productivities of 1.01, 1.38 and 1.03 g C m –2 d –1 were obtained for bamboo, hizol and kanchi substrates, respectively. Taxonomic composition of periphyton showed a rapid development of a relatively stable community with few differences between the substrate types. In total, 56 genera of algal periphyton and 35 genera of phytoplankton were identified. Based on a periphyton productivity estimate of 2.2–2.8 g AFDM m –2 d –1, periphyton alone can sustain an estimated fish production of 5000 kg ha –1 year –1 through the addition of a substrate area equivalent to 100% of the pond surface area.