Distribution and feeding of the carnivorous copepod Paraeuchaeta norvegica in habitats of shallow prey assemblages and midnight sun

Paraeuchaeta norvegica was found to be widely distributed in the Norwegian Sea. They were least abundant in north-western areas, but otherwise no clear horizontal patterns appeared with respect to latitude, longitude or water mass. Females and males had similar vertical distributions. The highest concentrations of adults occurred at 400-500 m depth; they largely avoided the upper 50-100 m, even at night. Stages CIV and CV lived shallower in the water column than the adults, with the highest concentration between 100 and 300 m. Stages CII-CIII were most abundant at 50-100 m, while CI was distributed slightly deeper (maxima at 100-200 m). Potential prey were most abundant in the upper 100 m; i.e. shallower than P. norvegica. Numbers of fecal pellets produced by freshly collected adult females were relatively low (estimated at 0.7 pellets per individual on average for the entire sea), with maximal numbers for individuals captured in shallow waters. This suggests food limitation during summer, when food is concentrated in upper waters, and short and light nights limit nocturnal access to the shallow food resources. Pellets mainly contained copepod remains.