Maternal provisioning of offspring and the use of those resources during ontogeny: variation within and between Atlantic Salmon families

1, The size and proximate composition of eggs and alevins (larvae) were mea sured from six full sibling families of Atlantic Salmon (Salmo salar), at s ix stages between fertilization and first feeding. 2, Egg and alevin size measures (diameter, wet mass, dry mass) and proximat e composition attributes (water, protein, fat, energy) were all highly corr elated with each other (r = 0.89-0.99), suggesting that each is a reasonabl e surrogate for any other. 3, Most of the variation in egg size (95.0-97.0%) and composition attribute s (95.5-97.9%) was partitioned between, rather than within, females. Most o f this variation was attributable to differences in female size, owing to t he length of time spent at sea. 4, Fat, protein and energy content varied less on a relative basis (control ling for egg size variation) than on an absolute basis, suggesting that cer tain combinations of egg attributes are optimal regardless of egg size. 5, Stored fat decreased by 9.6 mug day(-1) before hatching but increased by 27.4 mug day(-1) after hatching. The increase after hatching suggests that alevins actively synthesize (probably from protein) and store lipids betwe en hatching and first feeding. 6. Stored protein decreased by 8.8 mug day(-1) before hatching and by 181.3 mug day(-1) after hatching. Assuming all metabolic energy was derived from stored protein, metabolic rate increased logarithmically from 0.115 3 day( -1) to 5.43 J day(-1). Rates of oxygen consumption estimated from protein l oss (6.09-288.9 mul O-2 d(-1)) were similar to those reported in studies th at measured oxygen consumption using respirometry. 7. Alevins appear to convert protein to fat, a change that their mothers we re unable or unwilling tin an evolutionary sense) to make. This may reflect the conflicting goals of parents and offspring for maximizing fitness.