Spatiotemporal environmental gradients shape early life stage fish densities, assemblage structure, and growth in river-reservoir ecosystems

Key Points

• This research aims to explore how varying environmental conditions in river-reservoir ecosystems affect early life stage fish densities and growth.
• Quantified relationships among density, assemblage structure, and growth rates of early life stage fishes across eight river-reservoir ecosystems.
• Measured environmental variables including temperature, flow, turbidity, and food availability.
• Analyzed data across different zones within the reservoirs (riverine, transition, lacustrine).
• Upstream zones of river-reservoir ecosystems had significantly higher densities of early life stage fishes (p < 0.001).
• Fish assemblage structure showed temporal variability due to seasonal changes in water temperature and spawning timing (p < 0.001).
• Size of fish increased downstream, with smaller fish in riverine and transition zones and larger fish in lacustrine zones (p < 0.001).
• Average growth rates among zones were similar but varied significantly among different fish taxa (p > 0.05).