Abstract
Fish roe products are extremely valuable for the food industry with beneficial properties for human health beyond basic nutrition. From a fish’s perspective, making good quality egg masses ensures the continuity of the species through successful reproduction. This is mainly because once the egg is ovulated and fertilized, it must independently sustain the nutritive needs of the future embryo. Hence in most cases during sexual maturation, female fish actively accumulate nutrients inside the developing eggs to form the future food source for the embryo, the egg yolk. As the most diverse vertebrate group, the yolk nutrient composition of fish roe can differ according to the reproductive biology of the species, along with the available dietary sources the broodstock have access to. This chapter discusses the mechanisms of egg yolk formation, the principal differences between eggs from marine and freshwater fish, and the possible implications of manipulating egg composition to benefit the food industry.