Preliminary Assessment of the Water Physicochemical Suitability for Macrobrachium vollenhovenii in the Ovia River, Edo State, Nigeria

Abstract

Inland waters serve as critical biodiversity hotspots supporting vital fisheries, yet they remain highly vulnerable to environmental degradation, which prompted this assessment of the Ovia River in Edo State, Nigeria—a key habitat for the commercially significant African river prawn, Macrobrachium vollenhovenii. The study utilized a synoptic sampling event during the 2024 mid-rainy season across four stations to analyze ten physicochemical parameters using standard APHA methods, subsequently calculating a Physicochemical Suitability Index (PSI) by normalizing these values against established optimal ranges for the species. Results revealed a robust PSI of 0.83, indicating a strong alignment between the river’s water chemistry and the prawn's physiological requirements, with stable mean values for temperature (27.68°C), pH (7.53), and BOD (2.62 mg/L). However, extreme spatial heterogeneity was observed in Nitrate levels, which exhibited a high Coefficient of Variation of 150.31% and a peak concentration of 5.12 mg/L at one station, suggesting localized nutrient enrichment. The study concludes that the Ovia River serves as an excellent natural template for modeling M. vollenhovenii habitats and hatchery systems, though the localized nitrate peaks necessitate immediate management intervention and further seasonal monitoring to establish a definitive Habitat Suitability Index.