The potential of periphyton-based culture of the native major carp calbaush, Labeo calbasu (Hamilton)

The project evaluated the effect of installing scrap bamboo ('kanchi') as a substrate for periphyton on growth and production of the indigenous major carp calbaush, Labeo calbasu (Hamilton). The impacts of fish grazing on the periphyton community were also assessed. Six ponds were used, three of whi ch were provided with kanchi poles (700 per pond, spaced 30 cm apart). Pond s were limed and fertilized and stocked with L. calbasu fingerlings (mean t otal length = 5.16 cm; mean weight = 2.10 g) at a rate of 10 000 fingerling s ha(-1) (75 fish per pond). There were no statistically significant differ ences in water quality between treatments, although differences in phytopla nkton community composition were observed. Zooplankton numbers were the sam e in both treatments. While there was clear evidence that periphyton was be ing exploited by the fish, Chlorophycae being most affected, grazing was in sufficient to cause significant reductions in total periphyton densities. F ish survival and specific growth rates (SGRs) were significantly higher in ponds with substrates, production in treatments with and without scrap bamb oo substrate being 712.90 and 399.11 kg ha(-1), respectively, over the 120- day period. However, production in both treatments was low in comparison wi th other studies, water temperatures (23.6-32.7 degrees C) being less than optimum for growth. It was concluded that kanchi and other locally availabl e materials might be used to increase the production of some species of fis h, although further evaluation of production economics is required.