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

Intraspecific differences in female attributes influence egg quality and, a s a consequence, offspring viability. To further investigate this hypothesi s, we compared female attributes, egg size, biochemical egg composition, an d survival potential of offspring from 20 female spawners of an endangered rheophilic cyprinid, Chondrostoma nasus. Egg size was strongly related to f emale age and size. The chemical composition of egg dry matter was influenc ed by female size to a lesser extent. No significant relationship between e gg size and egg dry matter composition was observed. Mortality curves revea led three distinct periods of elevated mortality: early mortality, hatching mortality, and starvation mortality, separated by periods of reduced morta lity. No significant correlations between embryonic mortality (early mortal ity and hatching mortality) and egg size were found. Starvation mortality w as size selective: resistance to starvation correlated significantly with e gg size and egg energy content. The direct and indirect relationhips betwee n female attributes, egg quality, and offspring viability show that the two main components of offspring viability (embryonic mortality and larval res istance to starvation) are not interrelated and that the sequence female at tributes - egg size - larval resistance to starvation is the main pathway a long which size selectivity operates.