Effects of female attributes and egg properties on offspring viability in a rheophilic cyprinid, Chondrostoma nasus

Abstract

Intraspecific differences in female attributes influence egg quality and, as a consequence, offspring viability. To further investigate this hypothesis, we compared female attributes, egg size, biochemical egg composition, and survival potential of offspring from 20 female spawners of an endangered rheophilic cyprinid, Chondrostoma nasus. Egg size was strongly related to female age and size. The chemical composition of egg dry matter was influenced by female size to a lesser extent. No significant relationship between egg size and egg dry matter composition was observed. Mortality curves revealed three distinct periods of elevated mortality: early mortality, hatching mortality, and starvation mortality, separated by periods of reduced mortality. No significant correlations between embryonic mortality (early mortality and hatching mortality) and egg size were found. Starvation mortality was size selective: resistance to starvation correlated significantly with egg size and egg energy content. The direct and indirect relationhips between female attributes, egg quality, and offspring viability show that the two main components of offspring viability (embryonic mortality and larval resistance to starvation) are not interrelated and that the sequence female attributes - egg size - larval resistance to starvation is the main pathway along which size selectivity operates.