The bioaccumulation and toxic effects of heavy metals have caused ecological damage to aquatic ecosystem. In this study, concentration of heavy metals including zinc, lead, cadmium, iron, and copper were determined in the sediment and water as well as in the muscle, gill, and intestine of two fish species (Pelmatochromis guentheri and Pelmatochromis pulcher) of Mbaa River in Southeastern Nigeria. Samples were collected at three different spots from the river, and the level of heavy metals specified above were determined by atomic absorption spectroscopy (AAS) after a modified wet digestion process. The results indicated that sediment had the highest concentration of the heavy metals investigated while water had the lowest concentration. Fish tissues showed appreciable bioaccumulation of these metals as evidenced by a higher concentration profile when compared with that of water. Furthermore, the concentration of these heavy metals in water and their bioconcentration factor in the fish were above the recommended limit by WHO and FEPA, indicating that Mbaa River along Inyishi may not be suitable for drinking nor the fish safe for human consumption. The study also reveals the use of fish as bioindicator of aquatic environment.
The effect of replacing exotic broilers with indigenous chickens in vertically integrated homestead ®sh ponds as a means of improving the income status of the small-scale farmer was investigated. Ponds integrated at 1000 chickens ha ±1 provided the optimal water quality for ®sh survival and growth. Excreta load was 3600 kg ha ±1 month ±1 (dry matter); water pH 8.6; total alkalinity 65.0 mg L ±1 ; dissolved oxygen 8.0 mg L ±1 ; biochemical oxygen demand (BOD) 2.0 mg L ±1 ; ammonia 0.02 mg L ±1 ; total phosphates 10.0 mg L ±1 ; primary produc tivity 86 mg C m ±2 h ±1 ); biomass chlorophyll a 9.8 mg cm ±3 ; and standing crop 2.85 Q 10 3 cells mL ±1 . Fish recovery, weight gain and total yield (18.25 tons ha ±1 ) for Heterobranchus longi®lis, Valenciennes 1840, and 14.90 tons ha ±1 for Oreochromis niloticus (Linnaeus 1758) exceeded the production (3.50 tons ha ±1 and 2.10 tons ha ±1 , respectively, for H. longi®lis and O. niloticus) from ponds integrated with broiler chicken at the current optimum stocking rate of 1500 chickens ha ±1 . Indigenous chickens offered higher resistance, accepted crop wastes and trash as food and generated an excreta load similar to that from more expensive broiler chickens. Economic analysis of the ventures revealed substantial net income at all levels of poultry integration with indigenous chickens as against a net de®cit of ±= N210 000 ($2470.6) incurred by the farmer using exotic broilers. From a cost±bene®t ratio of 1:2.6 in T 2 (1500 indigenous chickens ha ±1 ) and 1:0.6 in T 4 (1500 broilers ha ±1 ), a net income of = N1.60 ($0.019) accrued to the farmer from every = N1.0 ($0.01) invested in the integrated system using indigenous chickens as against a net de®cit of = N0.40 ($0.005) on invested capital using broiler chickens at the same 1500 chickens ha ±1 level of poultry integration.
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