The potential of periphyton-based culture of the native major carp calbaush, Labeo calbasu (Hamilton) M A Wahab 1 , M E Azim 1 , M H Ali 1 , M C M Beveridge 2 & S Khan 1 1 Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh, Bangladesh 2 Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, Scotland, UK Correspondence: M A Wahab, Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh, Bangladesh Abstract 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 ®sh grazing on the periphyton commu- nity were also assessed. Six ponds were used, three of which were provided with kanchi poles (700 per pond, spaced 30 cm apart). Ponds were limed and fertilized and stocked with L. calbasu ®ngerlings (mean total length = 5.16 cm; mean weight = 2.10 g) at a rate of 10 000 ®ngerlings ha ±1 (75 ®sh per pond). There were no statistically signi®cant differences in water quality between treatments, although differences in phytoplankton community composition were observed. Zooplankton numbers were the same in both treatments. While there was clear evidence that periphyton was being exploited by the ®sh, Chlorophycae being most affected, grazing was insuf®cient to cause signi®cant reduc- tions in total periphyton densities. Fish survival and speci®c growth rates (SGRs) were signi®cantly higher in ponds with substrates, production in treatments with and without scrap bamboo sub- strate being 712.90 and 399.11 kg ha ±1 , respec- tively, over the 120-day period. However, production in both treatments was low in compar- ison with other studies, water temperatures (23.6± 32.7 °C) being less than optimum for growth. It was concluded that kanchi and other locally available materials might be used to increase the production of some species of ®sh, although further evaluation of production economics is required. Introduction The traditional `acadjas' of Ivory Coast, West Africa, and `kathas' of Bangladesh are brushpark-based ®sh-attracting devices (FADs) used by ®shermen (Welcomme 1972; Wahab & Kibria 1994). Dense masses of tree branches or bamboo are established in lakes, lagoons or rivers, and the ®sh are attracted by the provision of shelter from predators and a suitable habitat for breeding in which natural food is also abundant. In recent years, these ®sheries systems have served as models for novel periphyton- based aquaculture systems (Legendre, Hem & Cisse 1989; Konan, Soulemane & Abe 1991; Hem & Avit 1994; Konan-Brou & Guiral 1994; Guiral, Gour- bault & Helleouet 1995; Huchette 1997; Sankare, Kodjo & Kouassi 1997; Beveridge, Verdegem, Wahab, Keshavanath & Baird 1998). Konan-Brou & Guiral (1994) reported that the proliferation of periphytic species algal concentrations on the submerged branches led to an eightfold increase in algal standing crop within the `acadja' compared with the lagoon waters. Furthermore, it is evident that food intake per unit time per ®sh can be many times higher when plant material is offered as periphyton rather than as phytoplankton (Demp- ster, Beveridge & Baird 1993; Dempster, Baird & Beveridge 1995). Periphyton-based aquaculture systems offer the possibility of increasing both areal primary produc- tion and food availability. In a resource-constrained country such as Bangladesh, where more than 75% of households spend 90% of income on basic needs (BBS 1995), many cannot afford to provide even R # 1999 Blackwell Science Ltd 409 Aquaculture Research, 1999, 30, 409±419