178 DISCOVERY REPORTS 



greater part coming from the Weddell area. The whaHng grounds he in the lee of 

 South Georgia, and it is here, in the shelter of the island, that the Euphausians are able 

 to congregate. 



Turning now to the records for individual seasons, illustrated for Fin whales in 

 Plates VII to XIV and for Blue whales in Plates XV to XXII, it will be seen at once that 

 there is great variation in the positions of the centres of concentration. Some part of 

 this variation is no doubt to be attributed to irregularities in the arrival of different 

 schools of whales. It has been ascertained at the Marine Biological Station^ that there is 

 no steady flow of whales on to the whaling grounds during the course of the season ; on 

 the contrary, the whales tend to arrive in batches, usually rather closely aggregated, of 

 one species, and often with one or other sex or with immature predominating. As some 

 schools arrive others may be leaving, and it is probable that certain schools remain 

 longer on the grounds than others. 



But when allowance has been made for these considerations, there still remain certain 

 obvious differences in the distribution of whales in the seasons under review, and it 

 appears that the most significant difference is to be found in the latter half of the season. 

 In some years, in January and February, there is a very definite movement to the south- 

 western side of the island, while in other years no trace of this movement is to be seen. 

 In seasons 1924-5 and 1925-6 (Plates VIII, IX, XVI, XVII) there is no trace of this 

 southward movement in either species, both of which show in the later months a 

 remarkably heavy concentration close inshore to the north-east of the island. In 

 1923-4 and 1927-8 (Plates VII, XI, XV, XIX) both species show a movement towards 

 the south-west. In 1926-7, when Blue whales preponderated, the concentrations of 

 this species (Plate XVIII) shift round the ends of the island in the later months, but the 

 movement is less marked in Fin whales (Plate X). In 1928-9 the abundance of the two 

 species was reversed: Fin whales, which were very numerous, moved to the south 

 (Plate XII), while this movement is not clearly shown by the smaller numbers of Blue 

 whales (Plate XX). The data for seasons 1929-30 and 1930-1 do not give conclusive 

 results : whales were scarcer and the area covered by the catchers had greatly increased ; 

 but except for Blue whales in 1929-30 there are indications that both species tended to 

 move to the south in February and March. 



Summarizing the observations it will be seen that when either species occurs in 

 abundance it has moved to the south-western side of the island in the latter half of the 

 season, and that the only exceptions to this statement are the two outstanding seasons 

 1924-5 and 1925 6. The dense inshore concentrations in these two seasons are perhaps 

 to be explained in terms of hydrology and plankton; but unfortunately the research 

 ships began their work at the end of the 1925-6 season and full surveys of the conditions 

 on the South Georgia whaling grounds only date from 1926-7. 



Sir Sidney Harmer, in his valuable account of " Southern Whaling",- has shown that 



1 Mackintosh and Wheeler, Southern Blue and Fin Whales, Discovery Reports, I, pp. 458-60 (1929). 

 - Loc. cit., p. 131. 



