Environmental Drivers of Nile Tilapia (Oreochromis niloticus) Abundance in Lake Buluan: A Principal Component Analysis of Physicochemical Water Parameters

Abstract

Understanding the environmental factors that influence fish abundance is essential or sustainable fisheries management in tropical freshwater ecosystems. This study investigated the environmental drivers of Nile tilapia (Oreochromis niloticus) abundance in Lake Buluan, a major inland fishery in Mindanao, Philippines, using physicochemical water quality parameters and multivariate statistical analyses. Physicochemical measurements were collected from eight sampling sites representing littoral and limnetic zones. Fish sampling was conducted using standardized fishing gears. Principal Component Analysis (PCA) was employed to identify major environmental gradients, while a Generalized Linear Model (GLM) was used to evaluate the influence of these gradients on Nile tilapia abundance. The lake generally exhibited physiochemical condition suitable for freshwater fisheries, although notable spatial variation was observed among sampling sites. Nile tilapia was widely distributed throughout the lake. Results reveal distinct environmental gradients characterized primarily by variations in conductivity, temperature, pH, and turbidity. Additionally, Nile tilapia abundance was positively associated with conductivity and turbidity and negatively associated with temperature and pH. Furthermore, the primary environmental gradient significantly influenced spatial variation in tilapia abundance, whereas dissolved oxygen exerted comparatively limited influence under the observed conditions. The findings indicate that physiochemical water quality contributes to the spatial distribution of Nile tilapia in Lake Buluan. However, the relatively modest explanatory power of the model suggests that additional ecological and anthropogenic factors also influence abundance patterns. These results provide baseline information for fisheries management and support the integration of water quality monitoring into conservation and sustainable utilization strategies for Lake Buluan.

Understanding the environmental factors of fish abundance is important in sustainable fisheries management in tropical freshwater environments. This study monitored environmental factors of Nile tilapia (Oreochromis niloticus) abundance in Lake Buluan,a major inland fishery in Mindanao, Philippines, using physicochemical water quality parameters and multivariate statistics. Physicochemical samples were taken from eight sampling sites (littoral and limnetic areas). Fish were sampled using standard fishing gears. Principal Component Analysis (PCA) was applied to identify major gradients of environmental quality and a Generalized Linear Model (GLM) was applied to measure the impact of different gradients on Nile tilapia abundance. The lake was generally in good physiochemical condition for freshwater fisheries, but there is significant spatial variation between sampling sites. Nile tilapia was found to be common throughout the lake. We found a wide range of environmental gradients that are mostly affected by conductivity, temperature, pH, and turbidity. Nile tilapia abundance was also positively correlated with conductivity and turbidity, and negatively associated with temperature and pH. In addition, the dominant environmental gradient was also significant in terms of variation of tilapia abundance, whereas dissolved oxygen exerted comparatively limited influence under the observed conditions. This study clearly indicates that physiochemical water quality is involved in the distribution of Nile tilapia in Lake Buluan, but the low explanatory power of the model also shows that there are some other ecological and anthropogenic factors contributing to the abundance pattern. These findings provide a useful basis for fisheries management and support the incorporation of water quality monitoring for conservation and sustainable use of Lake Buluan.