The fecundity of dace, Leuciscus leuciscus (L.) in Emral Brook, Clwyd, North Wales

SUMMARY. Estimates of the fecundity of dace were made on 105 mature females using the dry method of Simpson (1959). The reliability of the counting procedure was assessed and found to be satisfactory. Fecundity was examined in relation to fork length (cm), somatic weight (g), ovary weight (g) and age (years). Logarithmic multiple regressions of fecundity on these variables showed that neither log fork length nor log somatic weight contributed significantly towards explaining the observed variations in fecundity. The best prediction equation for fecundity, incorporated both log ovary weight and log age. Incidents of extensive follicular atresia were found in the ovaries of 19% of the female dace examined and the frequency of occurrence of this phenomenon increased with age.