HORIZONTAL DISTRIBUTION, GROWTH AND DYNAMICS OF DISPERSAL 357 



The prevailing presence of the pack and all it implies, extreme cold, low photosynthetic values and 

 inferior grazing, is, I feel sure, the basic factor responsible for the slowing up of the growth-rate in 

 the East Wind zone. It is interesting, therefore, to record that much farther north among the young 

 swarms encountered in, at the edge of, or very close to the pack-ice during our winter and spring 

 surveys of the South Georgia whaling grounds in August, September and October of 1928, a cor- 

 responding slowing up of the growth-rate can readily be detected. The length and stage frequencies 

 of the young swarms encountered then together with those of the November survey of 1930^ are 

 shown in Fig. 108, the pack-ice or near pack-ice swarms being distinguished by an asterisk. 

 From August to November it will be seen that whereas in the open sea there is a steady, if at first 

 slow, upward trend in both growth and development, in or near the pack, there is a pronounced 

 backward trend characterised by a marked lag in developmental condition and a general inferiority 

 in modal length. 



Our knowledge of the speed of the East Wind drift is meagre. Weddell (1827) records a west by 

 northerly set of 31 miles in 3 days in 72° 38' S, 35° W, McNab (1839) a westerly set of 12 miles a day 

 near the Balleny Islands, Ross (1847) a south-westerly set of 7 miles a day in 68° 34' S, 12° 49' W and 

 speeds of from 9 to 18 miles a day for the cyclonic movement in the Ross Sea. Bruce (1918) mentions 

 north-westerly sets of from 10 to 12 and of from 12 to 18 miles a day near 67° S, 37° W, Fuchs (1958) 

 reporting a west-north-westerly set of between 1 5 and 20 miles a day in approximately the same position. 

 Near the Japanese base, Syowa, in 40° E, the westerly current is estimated to be travelling at some- 

 thing over 9 miles a day (Fukuoka, 1959). In the Australian quadrant of the East Wind zone a strong 

 westerly set of up to 15 miles a day was reported for two days following an easterly gale, the observa- 

 tions of the 'Aurora', spread over three voyages, being 'overwhelmingly in favour of a westerly drift 

 averaging 6 or 7 miles per day with a slight northerly component' (Mawson, 1940a:). It seems, how- 

 ever, that it might be moving faster near the coast, in the narrow belt where the larvae are concen- 

 trated, than farther out to sea. Westerly (or in the east Graham Land region north-westerly) coastwise 

 currents setting at from 24 to as much as 72 miles a day- have in fact been reported (Donald, 1896; 

 Antarctic Pilot, 1930; Deacon, 1937) from which it might be concluded that the coastal waters in these 

 high latitudes are moving with a speed at least comparable with, if not faster than, that of the Weddell 

 drift, and that the larvae they carry, westwards into the Weddell Sea and north-westwards out of it, 

 move at much the same resultant rate, approximately 8-14 miles a day, as they do in the more 

 northerly east-going stream. At 8 miles a day it might be expected that larvae having their origin in 

 risings such as those, for example, recorded in 0° off the Princess Martha Coast at the beginning of 

 March (p. 303, Fig. 71), moving coastwise round the Weddell Sea and developing as they went, would 

 eventually turn up in Weddell West, a journey of approximately 2200 miles, in a matter of 275 days, 

 or some 9 months after their original advent at the surface. During this time, if our estimate for the 

 high southern larval growth-rate is correct, they would have developed to a dominantly Sixth Furcilia 

 stage and it is interesting, therefore, to record that at the time and place expected, in November about 

 half-way along Weddell West, we did in fact encounter two mixed larval and adolescent swarms in 



1 Based throughout on the comprehensive measurements and stage frequency determinations of Fraser (1936, 

 Appendix i). 



2 Priestley (1923) reports even higher speeds off the Spit at Cape Adare, noting that in summer and autumn 'icebergs 

 of some size come sweeping past the Spit at a rate which at the full of the tide may reach a maximum of 3 or 4 knots'. The 

 current runs particularly strongly along the Ross Ice Barrier face, the 'Terra Nova' (Debenham 1923, end map 11) reporting 

 a westerly set there of as much as 3 knots. Scott (1905) mentions a berg here that had travelled 70 miles to the west in 12 days, 

 adding 'but the surface water had been moving at a greater speed, as we could tell by its effect on the ship'. Recent Japanese 

 observations on the movements of Antarctic icebergs (Kumagori and Yanagawa, 19586) suggest that the westerly set 

 experienced by Scott was probably of the order of | knot. 



