Fitness consequences of variation in egg size and food abundance in brook trout Salvelinus fontinalis

Egg volume was positively correlated with juvenile size at hatching and size at yolk sac resorption but had no significant effect on embryonic survival or development time. Juvenile survival was linearly related to egg size throughout the first 50 days of exogenous feeding at high and low food levels. Decreased food abundance significantly increased mortality among the smallest eggs but had a negligible effect on the largest eggs. Maternal fitness is a curvilinear function of egg size; food supply influences both the height and the shape of the function. Selection apparently favors an increase in offspring size with reductions in resource abundance. -from Author