Fish response to environmental stressors in the Lake Victoria Basin ecoregion

Freshwater organisms face multiple threats associated with habitat degradation, pollution, and eutrophication, in addition to overharvesting and species invasions. Furthermore, there is mounting evidence that freshwaters are highly sensitive to climate change. This chapter provides an overview of contemporary environmental changes in inland waters of the Lake Victoria Basin (LVB) ecoregion of East Africa with a focus on climate change, eutrophication, and land use. Case studies of fishes in the Lake Victoria basin and swamp-river systems of Western Uganda are used to explore potential effects of these stressors on morpho-physiological, performance, and fitness-related traits. Overall, fishes in the LVB ecoregion show acclimation capacity in upper thermal tolerance and aerobic performance, and adaptive plasticity in traits related to hypoxia tolerance (e.g., gill size). However, a trait-based climate change vulnerability assessment revealed that over 70% of LVB ecoregion fishes are vulnerable to climate change; and fish kills associated with turnover events or anoxic upwellings highlight the danger of rapid change in dissolved oxygen for some species. Plasticity may allow some fishes to persist in the face of multiple stressors in the LVB ecoregion. However, there may be consequences for fitness-related traits such as body size that could affect demographic stability and contributions of fish to food security.