Influence of Physico-Chemical and Nutrient Parameters on Fish Occurrence and Community Structure in Nguru Lake, Yobe State, Nigeria

The present study evaluates the influence of physico-chemical and nutrient parameters on fish community structure and occurrence in Nguru Lake, Yobe State, Nigeria, over a one-year period (January-December, 2022). Fish and water samples were collected monthly, from three randomly selected locations (Badum, Azur, and Farin Ruwa) in the lake. Physico-chemical parameters such as pH, temperature, dissolved oxygen, turbidity, electrical conductivity, and key nutrients (nitrate, nitrite, phosphorus, potassium, and ammonia) were measured in triplicate using standard procedures. Fish species composition was presented using descriptive statistics, while diversity was analyzed using biological indices, including the Shannon-Weiner, Species Evenness, and Margalef's Indices. The data obtained from the fish and water samples were further explored through Principal Components Analysis (PCA) and Canonical Correspondence Analysis (CCA) to evaluate the impact of environmental variables on fish distribution. The results of the physico-chemical parameters showed fluctuating values, though they are within the range for optimal fish growth, likewise the values of the analyzed nutrients. A total of 2654 individuals belonging to 51 fish species and 18 families, dominated by Cichlidae, which recorded 1,459 individual fish, representing 54.97%, were observed. Diversity indices indicated a moderately diverse and stable ecosystem, although elevated nutrient concentrations, particularly nitrogen and phosphorus, suggested potential stressors. CCA revealed significant correlations between nutrient levels and fish species distribution, indicating that nutrient levels, particularly nitrogen and phosphorus, play a critical role in shaping fish community dynamics. The findings highlight the need for sustainable lake management practices to conserve biodiversity and support fisheries productivity.