Discovery reports (1937) Discovery reports discoveryreports16inst Year: 1937 406 DISCOVERY REPORTS In Calanus acutus we have the same results again, but the difference between the summer and winter level is even more marked than in the other two species. In winter it appears to have been entirely confined to depths exceeding 500 m., and the main concentration may well have been even deeper than 1000 m. and so have been missed by the nets. In summer the vast majority again are at depths of less than 250 m. Enor- mous numbers occurred at St. 1273 between o and 100 m., but at St. 1271 no actual
Discovery reports (1937) Discovery reports discoveryreports16inst Year: 1937 406 DISCOVERY REPORTS In Calanus acutus we have the same results again, but the difference between the summer and winter level is even more marked than in the other two species. In winter it appears to have been entirely confined to depths exceeding 500 m., and the main concentration may well have been even deeper than 1000 m. and so have been missed by the nets. In summer the vast majority again are at depths of less than 250 m. Enor- mous numbers occurred at St. 1273 between o and 100 m., but at St. 1271 no actual concentration appears at the surface. Fig. 8. Winter and summer stations in the Scotia Sea. Thus we find all three species in deep water in winter and in shallow water in summer. The summer distribution is not so clearly brought out at St. 1271 as at St. 1273, but these two stations may be appropriately compared with Sts. 1222 and 1223 in 8o° W (see Figs. 5-7, vertical sections for December). The same three species showed the normal summer concentration near the surface at St. 1223 but were deeper and scarcer at St. 1222. It seems that in the higher latitudes the winter distribution persists into the early part of the summer, and it may be pointed out that St. 1271 is well to the south of St. 1273. It has been shown now that in three different parts of the Antarctic—in the south-east Pacific (8o° W), in the north part of the Scotia Sea, and in the south-west Pacific— Rhincalanus gigas, Eukrohnia hamata and Calanus acutus (or at least the adult and sub- adult members of these species) were found mainly to inhabit the upper layers of the water in summer and the deeper water in winter. Ommanney (1936, p. 296) also finds
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