Abstract
The effect of aquacultural practices on the bottom sediment quality of six selected earthen fishponds in Ife North Local Government Area of Osun State was investigated for a period of two years. The fishponds were grouped with regard to fertilization practice and water flowage regime into three sets comprising two fertilized non-flow-through ponds (FNF); two fertilized flow-through ponds (FF) and two unfertilized flow-through ponds (NFF). The investigated sediment quality parameters include color and textural composition, salinity parameters, major ions, organic parameters and heavy metals using standard methods. The parameters were not statistically different (P > 0.05) for the three sets of fishponds with the exception of calcium which was significantly available in the fertilized flow-through pond. The fertilized ponds were however richer in nutrient and of better drainage quality than the unfertilized ponds. The parameters with higher mean in the fertilized ponds (FNF and FF) were 16% higher on average and flow-affected parameters were 67% higher on average in the flow-through ponds (FF and NFF), of which 7.00-fold higher lead concentration contributed most to this situation. Of these parameters, cations, anions, micronutrients were found to be of highest mean concentration in fertilized flow-through ponds. However, the presence of significant levels of calcium ions as well as minimal accumulation of clay, silt and nutrients in fertilized flow ponds made this fish culture method most suitable.
Highlights
The pond bottom sediment is the storehouse in the pond ecosystem
The decomposition processes occurring in aquatic sediments helps to recycle nutrients and during the process, elements such as nitrogen, phosphorus, iron, cobalt, and copper are interchanged between sediment and the overlying water (Tsadu 1998)
The fish ponds assessed belong to Niger Feeds and Agricultural Operations Limited (NIFAGOL), which is a commercial fishing company in YakoyoOrigbo, Ife North Local Government Area (LGA), Osun State, Nigeria
Summary
The pond bottom sediment is the storehouse in the pond ecosystem. good bottom sediment and high-water quality are essential for successful pond management (Muendo et al 2014). Factors associated with aquaculture practices such as liming, fertilization, exogenous feeding of fish, fish excrement, dead fish and increased vegetation cause organic accumulation in the pond ecosystem and affect the physical and chemical properties of the bottom sediment (Boyd et al 2002). These pollutants are preserved in the sediment over a long period dependent on their chemical persistence and physico- /bio- chemical characteristic of the sediment (Singare et al 2011). The decomposition processes occurring in aquatic sediments helps to recycle nutrients and during the process, elements such as nitrogen, phosphorus, iron, cobalt, and copper are interchanged between sediment and the overlying water (Tsadu 1998)
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