COPEPODA 127 



Calarms aciitus, Giesbr. This species was the most abundant of all the larger Copepoda 

 in our collections. The complete record of its occurrence is given in Appendix II. For 

 the December-January South Georgia survey, 1926-7, the average number per 50 m. 

 haul with the N 70 V net in the top 250 m. of water was 152, whilst the maximum 

 number per 50 m. haul was 2075. 



Farran (1929) in his report on the Terra Nova Copepoda writes: 



This is the most characteristic antarctic copepod in the collection, being more plentiful than either 

 Calanus propinquus or Metridia Gerlachei. The few specimens from north of 60° S appeared to have 

 been dead when taken and the most northerly point from which it can definitely be recorded as living 

 is in 6i° 22' S. 



It was taken also by the Belgica, 1 National Antarctic (Discovery), 2 Scotia 3 and 

 Gauss 4 Expeditions, in the Antarctic. Ottestad (1932) writes: 



The expedition with S.S. 'Vikingen' 1929-30 to the Weddell Sea found Calanus acutus at all 

 stations. The northernmost location is situated at 54° 27' S and there is no sign of the species found 

 having been dead. From the existing data it may be concluded that Calanus acutus is a typical 

 Antarctic species, and that the most northern limit of its distribution lies between 50 and 6o° S. 



Whilst a few specimens were taken at St. 9 as far north as latitude 46 S, two at 50-om. 

 in water temperature of 6-8-7-2 C. and three at 250-100 m. in water temperature of 

 3-5-4-7° C, and a few at St. WS 70 against the Falkland Islands, the true Antarctic 

 nature of the species is clearly shown in Fig. 65. Here the vertical distribution of 

 the species on the oceanic lines between South Georgia and the Falkland Islands and 

 South Georgia and Tristan da Cunha is shown, and the marked contrast on either side 

 of the Antarctic Convergence, which lies between Sts. WS 67 and WS 68 on the former 

 line, and Sts. 10 and 11 on the latter line, is most striking. On the Falkland Islands 

 line it is seen at the lower depths of Sts. WS 68 and 69, being carried below the sub- 

 Antarctic water. Fig. 65 should be compared with the temperature and salinity curves 

 shown in Figs. 9 and 10. This almost complete limitation to the Antarctic Zone is 

 also seen in Fig. 63, where the general distribution in the area is shown, it being 

 particularly abundant at St. 161 far to the south-west of South Georgia. Immediately 

 round South Georgia it was distributed equally in water of both Bellingshausen Sea 

 and Weddell Sea origin, but was more abundant to the west, south and east than to the 

 north. 



Its seasonal distribution may be gauged, admittedly on slender material, by comparing 

 the C lines taken in November 1926, December 1926, March 1926, and May 1927, 

 when the average numbers per 50 m. haul with the N 70 V net for the top 250 m. from 

 the five stations in each season were 64, 112, 232, and 5 respectively, showing an increase 

 towards late summer and a falling off on the approach of winter. 



Its mean vertical distribution at both shallow and deep-water stations is shown in 

 Fig. 55. It was rarely abundant in the top 50 m., but was taken in the larger numbers 

 between 50 and 250 m. ; it occurred in small numbers in hauls between 2000 and 1000 m. 

 The depth distribution round South Georgia is shown in Fig. 64. No vertical diurnal 

 migration was apparent from our results; this is further discussed on p. 236. 



1 Giesbrecht (1902). 2 Wolfenden (1908). 3 Scott (1912). 4 Wolfenden (191 1). 



17-2 



