RHINCALANUS GIGAS 349 



spawning, in sub-Antarctic water. The age of the stock suggests that it had resulted 

 from a considerably later spawning than that which gave rise to the stock on the 

 Antarctic side of the convergence (St. 1 125). 



Weddell Sea, March 1933 (Fig. 29, Table VI /) 



During March a line of stations was taken from South Georgia to the pack-ice edge in 

 69° 22' S and 9° 27-5' E. The Rhincalanus population was analysed at six of these sta- 

 tions. Three of the stations, at which the catches were analysed into stages, were in water 

 flowing north-eastwards out of the Weddell Sea towards the South Sandwich Islands as 

 the Weddell Sea current (Sts. 1138, 1142 and 1144), and three were taken in the East 

 Wind Drift current flowing westwards into the Weddell Sea along the coast of Coats 

 Land (Sts. 1148, 11 50 and 1152). 



At the first group of stations, those in water flowing out of the Weddell Sea, the stock 

 consisted mostly of stages iii and iv. St. 1 138 was situated near the boundary between 

 Weddell Sea water and water of Bellingshausen Sea origin. The average temperature 

 was 076° C. ("oldest" Weddell Sea water), and it is therefore probable that the stock 

 at this station contained a mixture of the populations of the Bellingshausen Sea current 

 and of the Weddell Sea current. We saw that at St. 1131, a little over a week earlier near 

 South Georgia, the population also consisted of stages iii and iv, so that the probability 

 is that the same population was sampled at both these stations. At St. 1 142, where the 

 catch occurred only in the lower net, the stock consisted almost entirely of stage iv. The 

 temperatures of the surface 200 m. at this station show that it was worked in a tongue of 

 warm water moving south from the north (Deacon, 1936), so that the stock found in the 

 lower nets probably originated in the South Atlantic. It is very similar in its constitution 

 to that at Sts. 1138 and 1131, and it thus seems extremely probable that the populations 

 sampled at Sts. 1 138 and 1 142 are similar in origin and are carried into the Weddell Sea 

 by warm deep water from the South Atlantic. At St. 1144 there is a northerly move- 

 ment at the surface and a southerly movement from the Atlantic in the lower levels, 

 which is strongest at about 400 m. (Deacon, 1936). This southerly movement, however, 

 is less perceptible at St. 1144 than at St. 1142. The catches of R/iincalatius at St. 1144 

 were small, but it will be seen from Fig. 29 that the stock in the upper net, in water with 

 a northward tendency, was younger (stages iii and iv) than that in the lower net (mainly 

 stage v) which may be expected to have a mixed origin, part of the stock, at least, having 

 been carried southward in the lower layers. It will be noticed that the population 

 sampled by the lower net was similar in constitution to that found at the following 

 stations (Sts. 1148, 1150 and 1152) in the East Wind Drift current. The catch taken by 

 the upper net was too small for any definite conclusion to be drawn, but its age was 

 the same as that of the population sampled at the preceding stations (1138 and 1142). 

 It may be that it belongs to the same stock but, alternatively, it might perhaps suggest 

 that a spawning had taken place in Weddell Sea water very much later in the year than 

 in the Bellingshausen Sea current. On this point, however, the evidence is at present 

 insufficient. 



