The importance of egg size and egg energy density for early size patterns and performance of A rctic charr S alvelinus alpinus

The primary target of selection in most breeding programmes in aquaculture is to promote rapid growth while delaying maturation. In most cases, little is known about how such selection programmes may affect maternal provisioning of offspring and early development. Under favourable and predictable condition, which is typically the case in fish farming, females generally produce more but smaller eggs than wild females. By using a continuous range of egg size originating from females of a fourth generation of I celandic domesticated A rctic charr S alvelinus alpinus ( L innaeus, 1758), we assessed the relative importance of maternal effects and individual egg size for energy density of individual egg and several offspring traits from fertilization until 138 days post fertilization (dpf). We found that egg size and related energy density varied more among than within females. Although egg size was not correlated with energy density (at 1 dpf) or survival (at hatching and 138 dpf), it was positively correlated with most offspring traits throughout ontogeny. We further did not find any temporal variation in the correlation with the offspring traits during ontogeny. Within clutch variation in growth, yolk sac volume and hatching time were under the influence of direct female effects (maternal or genetic effects). These results show how egg size relates to individual performance in A rctic charr and constitute a baseline for understanding how domestication may alter offspring phenotypes early in life. These findings are discussed with regard to their consequences for aquaculture of A rctic charr and salmonids in general.