Kanningar av gongdini hjá fjarðarsild í Føroyum gjøgnum samdøgrið

Abstract

In october 1968 investigations on plankton and 1, 2 and 3 years old herring were carried out during 24 hours in Funningsfjørður, Faroe Islands. Plankton as well as herring showed vertical migration.

In daytime the main part of the herring and the plankton stayed from the bottom up to a level of 10 m below the surface, in the night they moved up from bottom coming to íhe surface entirely.

The echograms showing the movements of the herring form a picture corresponding with Ball's (1951) three step movement described for middle depths in the North Sea.  The only factor which the day and night migrations could be correlated with was the light intensity.

Stomach contents was found in the afternoon, whereas a sample of herring taken at 730 GMT, at sunrise, had empty stomachs only. The herring feed was composed of Acartia sp. besides some few Temora longicornis. Acartia longiremis and Acartia Clausii were dominating in the plankton samples, ohiefly females with egg sacks.