Predation and the evolution of vertical migration in zooplankton

TLDR: Examination of nonmigratory and migratory populations of a copepod in alpine clear-water lakes in the Tatra Mountains of Poland supports the view that migratory behaviour in zooplankton is selected for as a means of evading fish predators.

Abstract: Diel vertical migrations of zooplankton within water bodies have been related to efficient utilization of resources1–4 or to avoidance of mortality due to predation5,6. Although the possibility that vertical migrations evolved as an antipredator strategy has attracted much attention, no evidence has yet been presented of predation selecting for traits of migratory behaviour in planktonic animals. Therefore, I have examined nonmigratory and migratory populations of a copepod, Cyclops abyssorum, in alpine clear-water lakes in the Tatra Mountains of Poland. I report here that diel vertical migrations are not apparent in lakes without predatory fish, whereas short-range migrations are demonstrable in lakes which have been stocked with planktivorous fishes for decades, and long-range migrations are evident in lakes that have been stocked for centuries or millennia. These observations support the view that migratory behaviour in zooplankton is selected for as a means of evading fish predators.