Factors affecting the importance of myctophids in the diet of the world's seabirds

Mesopelagic myctophid fish are a key component of the world's ocean food webs, linking primary consumers and predators. Among marine predators, seabirds are globally significant consumers, but the extent to which they feed on myctophids has been investigated only at the regional scale. This global-scale review of analyses of the stomach contents of 228 seabird species reveals that the occurrence of myctophids in seabird diets is extremely variable. However, myctophids do constitute a considerable amount of the food of penguins, the Procellariidae (shearwaters/petrels, etc.), and storm-petrels; in locations where birds are foraging in oceanic basin/shelf slope habitat; and among birds that feed at night. Recent analyses of the fatty acid signature of stomach oil emphasize that myctophids can be important prey also for seabirds exploiting oceanic habitats. Current efforts to survey seabirds' distribution outside the breeding period, when they often become more oceanic, and their circadian activity may further support the global importance of myctophids as a pathway for carbon advection between marine compartments.