... DISCOVERY REPORTS 



442 



APPENDIX. TABLES 62-4 



I have presented the regional distribution and relative abundance of the krill, as it grows and spreads 

 round Antarctica, on a long series of maps in which increasing orders of abundance are represented 

 by circles of increasing diameter. Such a system, although widely used and on the whole perhaps the 

 most satisfactory we have for portraying distribution in plankton animals, lacks exactness, for orders 

 of abundance are very different from catch-figures, the higher orders, especially, often including 

 gatherings covering an enormous range of magnitude. The following tables are therefore presented 

 to show that the broad differences in regional abundance we repeatedly encounter throughout the 

 circumpolar sea, the richness of the East Wind-Weddell stream and the poverty of the West Wind 

 drift providing the most striking example, are revealed as equally striking phenomena when the 

 figures representing the harvest of our nets are treated more exactly. Using the gatherings of the 

 towed stramin nets, the horizontal (0-5 m.) net on the surface, the obUque (loo-o m.) net in the 

 surface layer (the catch-figures for the latter corrected as requisite as described on pp. 59 and 282-3), this 

 final presentation of the data is based throughout on observations confined to water where the krill 

 might be expected to occur; in other words it refers not to the circumpolar sea as a whole but only to the 

 region south of the 4° C isotherm (of the month of sampling), the thermal boundary which our 

 temperature data seem to show (see p. 76 and especially Tables 4, 5 and 9) is for all practical pur- 

 poses the absolute northern limit of the krill's geographical range. It deals mainly with the regional 

 distribution and relative abundance as a circumpolar phenomenon, showing (Table 62), sector by 

 sector, our average monthly and annual gatherings of the surface population in the Weddell Current 

 and in the West Wind drift, and again, sector by sector (Table 63), the corresponding gatherings in 

 the East Wind zone. It shows too (Table 64) something of the local distribution, presenting our 

 average monthly and annual gatherings round South Georgia and in the Bransfield Strait, where so 

 much of the early whaling took place. The numbers of net hauls from which the averages are derived 

 are shown throughout by italic figures. As in earlier presentations of the data (p. 65) the surface 

 population is divided into three broadly grouped developmental phases, larval (under 16 mm.), early 

 adolescent (16-20 mm.) and older adolescent and adult (over 20 mm.). Attention, however, is again 

 called to the apparent absence or great scarcity of the larvae in the Australasian, Indian Ocean and 

 Atlantic sectors of the East Wind zone, throughout a long coastal belt known (p. 302) to be an 

 important breeding ground of the krill. This is an anomaly that springs (p. 355) from the slow growth- J 

 rate of the euphausians in these high latitudes, where from February right through to April (p. 361, M 

 Fig. Ill) we find the larval population in the surface layer represented dominantly and almost^ 

 exclusively by the First Calyptopis, which, being very small, escapes as a rule through the meshes of 

 the stramin net. The complete absence of very young stages recorded in the Pacific sector between ^ 

 60° and 150° W seems on the contrary largely real, for there is little evidence that any substantial 

 spawning is going on there (p. 360). 



In the West Wind zone, although the overall poverty of the surface population is everywhere 

 pronounced, it will be seen that the scarcity of the three developmental phases, larval, adolescent and 

 adult, is not so clearly marked between 30° and 120° E as elsewhere, and that the larvae, although not 

 the older forms, seem to be gathered in some little strength in the Australasian sector and again in the 

 Scotia Sea. In these localities minor anomalies, or slight departures from the rule, are to be expected, 

 the Indian Ocean sector for instance being affected (p. 384) by spring overflow from the Weddell 

 stream, and, south and south-east of Kerguelen, by the branching of the East Wind stream, the 

 Australasian sector by another East Wind branching affecting the region north of the Balleny Islands. 

 In the Scotia Sea there are three factors to be considered, and all, either separately or in combination, 



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