The role of prey stratification in the predation pressure by the cydippid ctenophore Mertensia ovum in the Barents Sea

Abstract

The cydippid ctenophore Mertensia ovum occurs throughout the Norwegian arctic regions at least from the ice edge to the Arctic Circle. Using new data from the Barents and Greenland Seas, a simple model is constructed in which the upper boundary conditions for the trophic impact of Mertensia on populations of Calanus in this area are explored. Based on abundance data from MOCNESS and vertical net samples, experimental data on feeding and a range of typical values for the abundance of the principal copepod species, the range of probable predation pressure on copepods is calculated. Using typical abundances of the copepods and ctenophores in the Barents Sea, M. ovum appears to be capable of consuming a maximum of ca 1–5% d⁻¹ of the copepods in the water where it occurs. Vertical and horizontal spatial coupling probably plays a significant role in determining the extent of predation for this predator. Predation by other ctenophores may be a significant factor in its own biology.