Seasonal Variation in Fish Diversity and Abundance in Stratum VII of Lake Volta, Ghana

Abstract

Lake Volta, the largest man-made reservoir in Africa supports one of West Africa’s most important inland fisheries, yet ecological studies on seasonal variation of fish assemblages remain limited. The study assessed seasonal variation of fish assemblages in Stratum VII of Lake Volta, Ghana. Fish samples were obtained during wet and dry seasons from January to December 2023 and analysed for diversity indices, species composition and multivariate analysis using Primer 6. A total of 42 species, with slightly higher richness in the dry season (37 species) compared to the wet season (35 species) was recorded. Shannon diversity index values (2.05–2.06) and evenness (0.997–0.999) showed no significant seasonal differences, suggesting a stable distribution of individuals among species despite fluctuations in species abundance. Species abundance recorded during the wet season (1580 individuals) was higher than recorded during the dry season (722 individuals), showing functional recruitment driven by flood inflows. SIMPER analysis revealed that Chrysichthys walkeri, C. auratus, Schilbe mystus, and Synodontis sorex were the main contributors to seasonal dissimilarity (> 10%) in species abundance. More than 25 species were rare, potentially supporting ecological heterogeneity in Stratum VII of Lake Volta. Based on the findings, management measures such as seasonal closures, habitat protection, and livelihood diversification are recommended to mitigate seasonal shocks.