Empirical Investigation of the Effect of Pond Age and Soil Type on Fish Production Potential in Earthen Ponds in Kebbi State

The soil characteristics of earthen fish ponds strongly influence water quality, natural food productivity, and ultimately fish yields, yet empirical relationships between pond age, soil type, and fish production in North West Nigeria have not been quantified. This study empirically investigates the effect of pond age (1 to 10 years) and soil texture class on water quality parameters, phytoplankton and zooplankton abundance, natural benthic food availability, and Nile tilapia production in 36 earthen ponds across three districts in Kebbi State. Soil cores were collected from pond bottoms and banks and analysed for texture, organic carbon, total nitrogen, available phosphorus, and pH. Monthly water quality and plankton sampling was conducted over one production cycle. Fish production was measured at harvest, correcting for supplementary feed application. Results showed that ponds in clay-loam soils had significantly higher total dissolved nutrient concentrations and greater phytoplankton biomass than sandy-loam ponds, independent of age. Fish production in unfed clay-loam ponds averaged 420 kg/ha compared to 180 kg/ha in sandy-loam ponds. Pond age had a positive but diminishing effect on natural productivity up to year 6, attributed to accumulating organic matter in pond sediments. Beyond year 6, an inverse trend was observed, associated with sediment anaerobiosis. The study provides empirically derived soil-production relationships that can guide pond site selection and management recommendations for the Kebbi State Aquaculture Development Authority.

Keywords: earthen pond, soil type, fish production, water quality, Kebbi State