396 DISCOVERY REPORTS 



times as both spring and summer distributional charts reveal, carrying rare individuals of the over 

 20 mm. class up to and even over the convergence into the Subantarctic w^ater that lies to the west. 

 The complexity of the water movements responsible for these anomalous occurrences, which it 

 will be seen are confined to the Falkland sector alone, is discussed in greater detail on p. 76. 



In his analysis of the results of the Discovery Committee's whale-marking programme of 1932-8 

 Rayner (1940) finds a distinct tendency among fin whales of Area 11 (Brown, 1954, p. 359, Fig. i), 

 apparently during their summer sojourn on the feeding-grounds, to converge on Weddell West, 

 a movement, one is tempted to suggest, that could well be a deliberate seeking out of a region where 

 their food (Fig. 135) is in rich supply. He writes: 



Although it is fully recognized that whale-marks can only be recovered from those places where whaling is carried 

 out and that the positions and movements of the factory ships have a considerable bearing on the picture rendered 

 by the returned marks, it is also true that the factory ships do not remain long in areas where whales are not to be 

 found. It does, therefore, seem reasonable to suggest that the part of the mouth of the Weddell Sea lying between 

 35 and 50° W has, for some reason, a strong attraction for Fin whales, which congregate there from a wide area 

 extending to the east and west. In addition there seem to be strong grounds for considering the region between 

 30° W and 0° to be more sparsely populated with Fin whales. The reasons for this are obscure and a discussion of 

 the possibilities beyond the scope of this paper, but it might be suggested that the influence of the submarine 

 topography along the southern verge of the Scotia Sea on the hydrology of that region sets up conditions favouring 

 the production of rich food stores which attract the whales.^ 



In his more recent account of the progress of marking Rayner (1948) notes that additional marks 

 recovered since 1939 all corroborate the results arrived at in his earlier paper. 



Summer, then, is essentially a time when, of the three broadly grouped developmental phases of 

 the surface population, the larval, the early adolescent, and the older adolescent and adult, the third 

 alone, upon which the whales so heavily feed, is at the peak of its abundance, and at that peak is spread 

 throughout the feeding grounds to their farthermost geographical limits. It is a time on the other hand 

 (see again Figs, no and 1 24) when the larvae and early adolescents are limited both in their numbers and 

 geographical range, the main mass of the larvae, just launched on their surface existence, being con- 

 fined to the western Weddell drift but chiefly to Weddell West,^ the main mass of the early adolescents 

 (the small whale food), shortly about to outgrow themselves, surviving only in the East Wind zone. 



The developmental condition and length frequencies of the summer swarms, that contribute so 

 heavily to the annual fattening of the southern whales, are shown in Fig. 136. Taking in turn (a) the 

 situation in the northern or Weddell zone, and (b) the situation in the southern or East Wind zone, 

 the principal facts presented may be summarised as follows: 



{a) Northern zone 



(i) In summer the staple whale food is represented by a heterogeneous assemblage of yearling 

 (13-15 month old) and adult (25-27 month old) swarms, the yearhngs having all but outgrown their 

 early adolescent (11-20 mm.) phase. 



(2) In the yearling swarms the females are dominantly in stage i in January, stages i and 2 (rarely 3) 

 in February and stages i, 2 and 3 in March. In the adult swarms they are dominantly in stages 5, 6 

 and 7^ (rarely 8)'* in January, stages 6, 7 and 8 in February and stages 7 and 8 (predominantly the 

 latter) in March, the mounting frequency of stage 8 encountered as the summer advances indicating 

 that spawning is probably at its height towards the middle, rather than at the beginning, of the season. 



* Some discussion of the questions Rayner leaves unanswered is given on pp. 243-5. 



* Bearing in mind, however, the far southern region of larval abundance (p. 310, Fig. 74 and p. 311, Fig. 75) in the East 

 Wind zone which cannot be revealed by the stramin nets because the burgeoning surface population there, all through the 

 summer (p. 361, Fig. iii), consists so very largely of the small escaping First Calyptopis stage. 



^ Bargmann's stage 7 a or gravid. * Bargmann's stage 7B or spent. 



