The diet and growth of 0‐group dace, Leuciscus leuciscus (L.), and roach, Rutilus rutilus (L.), in a lowland river

The diets of 0‐group dace and roach in the Lower Welsh Dee were studied by stomach contents analysis of seasonal and diel samples. During development, dace preyed on a sequence of food types, initially being mainly carnivorous then becoming nocturnally carnivorous and diurnally omnivorous. Roach showed a similar pattern, although after the first two months of life they were more herbivorous/detritivorous. From the variations in the diets, it is hypothesised that both species are limited by food. This receives circumstantial support from their poor observed growth. The food supply routes by which flow regulation of the River Dee could affect juvenile fish production are noted.