Investigations on Zooplankton in Norwegian Waters and in the Norwegian Sea during 1957-58
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The variations in zooplankton volume at fixed stations along the coast of Norway, western Spitsbergen, and at st. "M" in the Norwegian Sea have been studied during 1957 and 1958. In 1957 the plankton was on the whole less abundant than in the previous year, and at Skrova the spring maximum also occurred one month later than in 1956. In 1958, the plankton volumes were again larger, except at st. "M". Peaks in volume were observed at Skrova in May and August, at Skarsvåg near North Cape, and Kongsfjord, western Spitsbergen, in July and September. Salps were abundant at Skrova and Skarsvåg in October 1958. Vertical hauls were taken with a Nansen net in coastal and offshore areas of northern Norway in July -August 1957. The plankton was as a rule very scarce, except in an area west and south of Bear Island, where about 11 ml per haul were taken, mainly Calanus finmarchicus. In the offshore areas farther south, Aglantha digitale dominated. A chart of the average stage distribution of C. finmarchicus revealed a picture very similar to that represented by the isotherms at 20 m level. Zooplankton was sampled in vertical hauls with a one metre net in the Norwegian Sea and adjacent areas in May-June 1958. The plankton was most abundant in the cold, northwestern parts of the sea, and off the coast of northern Norway. During most part of the cruise a shallow scattering layer was recorded on an echo sounder. The recordings were quantitatively charted. In relation to the quantitative distribution of zooplankton various discrepancies were found. By comparing the distribution of various plankton organisms with the echo recordings, it was found that the echoes probably were caused by fish fry and euphausiids, some possibly also by appendicularians and medusae. The average stage distribution of Calanus finmarchicus during the cruise in 1958 gives a picture very similar to that of the isotherms at 20 m.
SeriesFiskeridirektoratets skrifter, Serie Havundersøkelser
vol 12 no 6