State-dependent vertical distribution of the carnivore copepod Pareuchaeta norvegica

Abstract

We explored the impact of body condition on vertical distribution of the carnivore copepod Pareuchaeta norvegica. Individuals sampled in the upper part of the water column had lower dry weight and slightly shorter prosome than individuals sampled deeper. Non-ovigerous females occurred higher in the water column than ovigerous females. Our results suggest that ovigerous females and individuals with large energy reserves to a large extent prioritize predator avoidance in deep water versus feeding in the upper part of the water column compared to non-ovigerous females and individuals with low energy reserves. Adult females collected closest to the surface were less pigmented than those found deeper. This, however, proved to be a quickly adjustable trait depending on prevailing light conditions.