340 DISCOVERY REPORTS 



At the Station just south of the Antarctic convergence (St. 904) nearly a month 

 (20. vi) later than the stations above mentioned, on the line southwards from Mel- 

 bourne, we find the winter generation largely advanced to stage iv, though many stage iii 

 were still present. 



There are certain striking features noticeable in the analyses of the stock in these 

 winter months. One of these is the complete absence of adults from the catches after 

 the middle of April. Adults were almost entirely absent from the catches on the line 

 from Enderby Land to Fremantle at the end of April, when one would suppose that the 

 summer generation was approaching maturity and was about to spawn. They were 

 similarly quite absent in May, south of Australia, after spawning had taken place. As 

 already remarked, a study of the stations taken in April on the Cape Town to Enderby 

 Land line leads one to believe, though the evidence is admittedly slender, that the adults 

 descend from the surface towards the winter level earlier than the younger copepodite 

 stages (cf. upper and lower nets at Sts. 850 and 851, Fig. 25). One must assume that 

 the adults have sunk beyond the range of these nets by the end of April, while the 

 younger stages remain still within their range. It is hardly possible therefore to regard 

 the hauls on these two lines as representative of the populations in these areas. The 

 second striking feature of the catches during the winter was the swarm of very young 

 stages near the surface at the end of May at the edge of the pack-ice (St. 887), since 

 elsewhere at the same time of year small catches were being taken which appeared in the 

 lower nets only. It seems probable that the explanation of this lies in the peculiar 

 hydrological conditions existing at St. 887. This station was situated in the divergence 

 region (Deacon, 1936) exactly upon the boundary between the East and West Wind 

 Drift currents, where, owing to upwelling and mixing, warm deep water is carried up 

 to within 60 m. of the surface. It seems certain, from the position of the main mass of 

 the population at this time of year, at stations other than 887, that the winter spawning 

 during May took place below the 250-m. level in southward-flowing warm deep water, 

 out of range of the 250-100 m. net, but that at St. 887, near the edge of the ice, the 

 young forms were carried upward to within 100 m. of the surface in the upwelling warm 

 water. This is confirmed by the presence of stage iii in the lower net at St. 891, at almost 

 the same date, away from the divergence region, and of stages iii and iv in a similar 

 position about a month later. 



SUMMARY, SOUTH INDIAN OCEAN AND AUSTRALIAN SECTOR, 



WINTER MONTHS 1932 



1. In the South Indian Ocean the summer spawning in the season 193 1-2 apparently 

 took place later than in the Falkland Sector. 



2. The mid-winter spawning in the Australian Sector in 1932 took place during May 

 and the beginning of June. The winter generation was found in stage iii at the end of 

 May and stage iv in the middle of June in northern Antarctic waters. 



3. The winter spawning took place in southward-flowing warm deep water, but the 

 young products were found at one station (887), taken at the edge of the pack-ice, 



