Egg consumption in mature Pacific salmon (Oncorhynchus spp.)

Abstract

For over a century, conventional wisdom has maintained that Pacific salmon ( Oncorhynchus spp.) cease feeding when they return to freshwater rivers to spawn. Here, we overturn this belief by showing that multiple species of Pacific salmon consume eggs during spawning. Overall, 13% of stomachs contained eggs, and feeding rates were estimated at up to 14 eggs or 52 kJ per day. Feeding experiments revealed that mature salmon could digest eggs, as fed salmon maintained significantly higher body mass than unfed salmon. Such egg consumption presents a fundamental shift in our understanding of Pacific salmon ecology that may have important implications for migration and management models. Indeed, the energy from consumed eggs could allow salmon to migrate up to an additional 3.8 km upstream per day of feeding, or extend the duration of spawning activity by up to 12%. Furthermore, salmon stocks may have evolved local adaptations to their specific migration and spawning requirements that include nutrients from salmon eggs. Thus, successful salmon management efforts may need to preserve not only spawning habitat and migration corridors, but also feeding opportunities.