Abstract

Water hyacinth (Eichhornia crassipes) is an aquatic plant that has the capacity to absorb nutrients, making it a potential alternative for the management of fishpond water. The effect of this plant on the physicochemical properties of fish pond water and on the growth of African catfish was investigated in this study. Four plastic ponds 2.0×2.0×1.2 m deep were used for the study. Fifteen percent of the surface area of two of the ponds was covered with water hyacinth while the other two ponds, which served as the control, were left uncovered. African catfish juveniles, with an average weight of 0.3 kg, sourced from a commercial fish farm, were used to stock each of the ponds at a density of 30 m^-2. The fish were fed with commercial feed pellets at an average rate of 0.33 g/fish/day. Water samples were drawn from the ponds weekly and analyzed for relevant physicochemical parameters. Based on the observed oxygen content of the ponds, the water in the control ponds were changed every week while those of the ponds with water hyacinth were changed bi-weekly. Fish samples were randomly selected weekly from each pond and weighed to determine the fish growth. The study lasted for four weeks. Results showed that the mean concentrations of total dissolved solids (TDS), total hardness, Mg hardness, chloride, nitrate, nitrite, sulphate, conductivity, turbidity and dissolved oxygen (DO) were higher, but not significantly (P≤0.05), under water hyacinth cover. Other parameters such as ammonia and biochemical oxygen demand (BOD) were higher in the control pond. All parameters were fairly within the acceptable limits. There was also no significant difference (P≤0.05) between the final average weight of the fish in the ponds with water hyacinth (0.85 kg) and the control ponds (0.69 kg). Apart from reduction in water use, it would appear that the use of water hyacinth does not confer any significant advantage in fish ponds.

Key words: Fish pond, water hyacinth, Eichhornia crassipes, African catfish, physicochemical properties.