Effects of bamboo substrate and supplementary feed on growth and production of the African catfish, Clarias gariepinus

The effects of bamboo poles as substrate for periphyton development on the growth and production of the African catfish, Clarias gariepinus, was evaluated over a period of 90 days. Three treatments, namely manure application as control (C), control and substrate installation (C + S) and, control and substrate with supplementary feeding (C + S + F) were randomly allotted to six earthen ponds each with an area of 100m. Catfish fingerlings of mean weight 27.5g + 1.25 were stocked at the rate of 80 fish per 100m. Water temperature, pH, Total Alkalinity, Total Dissolved Solids (TDS), ammonia and nitrites were monitored during the study. The results obtained after a 90day culture period indicated no significant variations in water quality between treatments. Similarly, there were no significant difference in survival between the treatments which ranged from 81.3%, 96.8% and 86.3% for the C, C+S and C+S+F respectively. The mean gross fish yield (kg/100m) varied from 16.0kg for C + S, 9.5kg for C + S + F and 6.0kg for C. the study indicated bamboo poles as substrate for periphyton was a superior alternative to improve catfish production under pond conditions. @ JASEM The demand for fish in Ghana is increasing in response to the health benefits of fish and increasing human population. The relatively lower cost of fish compared to beef, chicken or mutton is also a contributory factor to the rising demand as most people can easily afford to buy fish or fish products. Fish is consumed by both rural and urban populations and it contributes about 60% of the animal protein intake of Ghanaians. Fish consumption per capita in Ghana is known to be as high as 20 kg compared to the world average of 13 kg per capita (MOFA, 2004). The expected fish demand in Ghana for 2007 is 913,992 tonnes. With the present production level of 511,836 tonnes per annum, there is an outstanding deficit of 402,156 tonnes (Mensah et. al., 2003). Although, fish is on high demand nationwide, consumption is greatly limited by insufficient production and supply. The Ghana government imports an additional USD 200 million worth of fish to meet the ever increasing domestic market demand. In pursuit of the national agenda to ensure responsible fisheries, food security and poverty alleviation through fish production to meet domestic consumption and for export, there is the need to focus on aquaculture since it has the potential to supplement the output from capture fisheries to meet domestic consumption and for export. Intensive aquaculture requires inputs that are frequently beyond the means of resource-poor rural farmers. Periphyton-based aquaculture can be practised wherever fish farming is possible (Azim et. al., 2001). It is considered the best practice of fish farming since it requires only cheap and readily available inputs, yet highly efficient. It is a flexible technique that originated from indigenous knowledge of brush park fisheries where bushy tree branches installed in water bodies served as a device for attracting fish for harvesting (Welcomme, 1972). From a theoretical viewpoint, the advantages conferred by adding substrate to an aquaculture system is an increase in the energy and nutrient transfer efficiencies of the system owing to the additive effects of the periphyton and phytoplanktonbased components of production. Herbivorous fish generally require larger-sized food sources such as benthic algae, alga-based detritus or higher aquatic plants, which can be harvested more efficiently as well as zooplankton to supplement the intake of phytoplankton by omnivorous fish. Hard substrates such as bamboo and other tree branches, which are generally absent in traditional fish ponds are essential component of the periphyton-based aquaculture for inducing bacterial and zooplanktonic biomass associated with alga growth. This abundant natural food is exploited directly by many herbivorous and omnivorous fish as a basic source of food (Azim et. al., 2001). In this study, a system of periphyton-based aquaculture was considered as an alternative to fish production in conventional, substrate-free, pond. The design of treatments focused primarily on improving fish yield through the use of minimal quantity of substrates, optimal level of fertilization with organic manure that will compensate for the small quantity of substrate used by inducing enough natural production, and the application of supplementary feed. Monoculture of an indigenous farmed species, catfish, was used with the principal aim of improving fish production in aquaculture systems. Against this background the study was conducted in order to Evaluate the effects of bamboo substrate and supplementary feed on the growth performance of the African catfish, Clarias gariepinus and assess the potential of periphyton-based aquaculture in improving fish production. Effects of bamboo substrate and supplementary feed on growth and production of the African catfish, Clarias gariepinus * Corresponding author: Amisah, S 26 26 MATERIALS AND METHODS The experiment was conducted in six earthen ponds at the experimental fish farm of the Department of Fisheries and Watershed Management of the Kwame Nkrumah University of Science & Technology, Kumasi, Ghana. The experiment consisted of three treatments: Control (C), control and substrate installation (C + S), and control and substrate with supplementary feeding (C + S + F). The control treatment consisted of fertilization with pig manure that runs through all ponds at the same rate. The second treatment, which was control with bamboo installation at the density of 4 poles per m, provided an additional mean surface area of 73.28m. The effect of these treatments on the culture system as well as yield of cultured species was examined at the end of a 90-day culture period between December, 2006 and February, 2007. Three 200 m earthen ponds were each partitioned with nylon nets into two to make up for the six ponds for the experiment. Each pond had an area of 100m with an effective water surface area of 80m and mean depth of 50m. Ponds were sun and air dried for three weeks, and planted with bamboo poles with mean diameters of 9.0cm and mean lengths of 90.0cm. Bamboo poles were driven vertically into the pond bottom at 1metre intervals, and yielded a total submerged area of 73.25 m per pond (Plate 1). Ponds labeled as 1, 2, 3 and 5 received the substrate treatments while ponds labeled as 4 and 6 were without bamboo poles. Plate 1.An experimental pond with installed bamboo poles at 1m