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

Early life stage fishes are susceptible to variation in environmental
gradients, which dictate growth and survival, ultimately shaping adult
assemblages. Creation of river-reservoir ecosystems (RRE) by impounding
rivers results in longitudinal zonation within the reservoir (i.e.,
riverine, transition, and lacustrine zones) and gradients owing to changes
in temperature, flow, turbidity, food availability, and physical
structure. We quantified relationships among density, assemblage
structure, size structure and daily growth rates of early life stage (ELS)
fishes and environmental conditions across zones of eight RRE in central
Ohio. We observed significantly higher densities in upstream zones of RRE,
correlated with increases in littoral and floodplain habitat (p <
0.001). Fish assemblage structure was similar across zones from river
inflows to the dam, but more variable temporally due to seasonal
differences in water temperature (p < 0.001), and spawning
periodicity. Fish size increased in a downstream direction with smaller
individuals in riverine and transition zones and larger individuals in
lacustrine zones (p < 0.001). Average growth rates did not differ
significantly among zones (p > 0.05) but varied among taxa. Our
results demonstrate that high-density nursery areas with more complex
habitats do not necessarily correspond with enhanced growth.