MIGRATIONS AND DISTRIBUTION 255 



a peak for Humpbacks but also a marked maximum of Fin whales and a smaller but 

 still distinct concentration of Blue whales. The significance of the high proportion of 

 Fin whales shot at compared with Blue and Humpback whales is discussed below 

 (p. 263, etc.). 



A preliminary analysis of some of the records of whales observed during the voyages 

 of the ' Discovery II ' is of some assistance here. These observations, however, are limited 

 and in certain respects unsatisfactory, and a little explanation is necessary. During the 

 voyages of the 'Discovery', 'Discovery II' and 'William Scoresby' it has been the 

 practice to record all whales seen, and, as far as possible, the date, time, position, species, 

 numbers in schools, direction of movement, etc., would be logged, together with the 

 name of the observer. The principal object of course was to gain information on general 

 distribution, abundance and movements, and to compare distribution with local 

 oceanographical conditions. It was evident from the beginning, however, that such 

 records were quantitatively unreliable. The vast majority of whales noted are seen as 

 distant spouts, and the number of such spouts which can be seen must depend in a 

 major degree on the ever-changing conditions of visibility. Estimation of the number 

 of whales in a school is also difficult, even at short range, and it is often uncertain 

 whether spouts seen at intervals are from the same whale or from several whales. This 

 risk of counting the same whale more than once is not of much importance when the 

 ship is steaming at normal speed on a straight passage, but causes much uncertainty 

 when she is doing intensive work in a limited area. Reliable identifications of species 

 are especially difficult (see p. 261) and have been far too few to give any idea of the 

 distribution of the species separately within the different areas. Unidentified whales, 

 however, can almost always be distinguished on the one hand as either Blue, Fin or 

 Humpback, or on the other hand as some smaller species such as a Minke. 



During the commissions of the 'Discovery' (1925-7) and the earlier work of the 

 'Discovery II' and 'William Scoresby', investigations were largely concentrated in the 

 limited whaling grounds of the Falkland Islands Dependencies, and in view of the un- 

 certainties involved, less importance was attached to direct observations on whales than 

 to the routine oceanographical research. Later investigations were spread over the 

 whole Southern Ocean, and in the third, fourth and fifth commissions of the ' Discovery 

 II ', when long voyages were arranged through the belt of ocean mainly inhabited by 

 whales, a special look-out, in addition to the officer of the watch, was continuously on 

 duty during passages suitable for such observations. For this reason the best com- 

 parable data are forthcoming from the ship's last three commissions (1933-9). Table 16 

 and Fig. 7 show the numbers of whales presumed to be Blue, Fin or Humpback, 

 estimated to have been seen south of 50 S between each io° of longitude during such 

 passages in the summer months. Many series of observations are omitted which for one 

 reason or another were not fairly comparable. Fig. 8 shows the route taken by the ship 

 on each occasion. Table 16 also gives the approximate time (to the nearest half-day) 

 spent by the ship in each io°, and finally the average number of whales estimated to have 

 been seen per day. Sometimes where large numbers of distant spouts were seen the 



