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

Abstract

Summary The size and proximate composition of eggs and alevins (larvae) were measured from six full sibling families of Atlantic Salmon (Salmo salar), at six stages between fertilization and first feeding. Egg and alevin size measures (diameter, wet mass, dry mass) and proximate composition attributes (water, protein, fat, energy) were all highly correlated with each other (r = 0·89–0·99), suggesting that each is a reasonable surrogate for any other. Most of the variation in egg size (95·0–97·0%) and composition attributes (95·5–97·9%) was partitioned between, rather than within, females. Most of this variation was attributable to differences in female size, owing to the length of time spent at sea. Fat, protein and energy content varied less on a relative basis (controlling for egg size variation) than on an absolute basis, suggesting that certain combinations of egg attributes are optimal regardless of egg size. Stored fat decreased by 9·6 µg day−1 before hatching but increased by 27·4 µg day−1 after hatching. The increase after hatching suggests that alevins actively synthesize (probably from protein) and store lipids between hatching and first feeding. Stored protein decreased by 8·8 µg day−1 before hatching and by 181·3 µg day−1 after hatching. Assuming all metabolic energy was derived from stored protein, metabolic rate increased logarithmically from 0·115 J day−1 to 5·43 J day−1. Rates of oxygen consumption estimated from protein loss (6·09–288·9 µl O2 d−1) were similar to those reported in studies that measured oxygen consumption using respirometry. Alevins appear to convert protein to fat, a change that their mothers were unable or unwilling (in an evolutionary sense) to make. This may reflect the conflicting goals of parents and offspring for maximizing fitness.