. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. MULTIPAROUS FEMALES 449 waters in January, and entered the pelagic catches in peak numbers in February. The ascending limb of the pelagic curve actually appears to be about one to two months later than the ascending part of the curve for South Georgia. In drawing this figure the scale, on which the estimated numbers of lactating females have been plotted, has been so arranged that the descending limb of these curves is in advance of the descending limb of the upper curve (which shows the approxi
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. MULTIPAROUS FEMALES 449 waters in January, and entered the pelagic catches in peak numbers in February. The ascending limb of the pelagic curve actually appears to be about one to two months later than the ascending part of the curve for South Georgia. In drawing this figure the scale, on which the estimated numbers of lactating females have been plotted, has been so arranged that the descending limb of these curves is in advance of the descending limb of the upper curve (which shows the approximate expected frequency of weaning), by about 2 weeks to a month. This is in order to allow for the fact that lactating females taken in antarctic waters are on average estimated to be only 2-4 weeks in advance of weaning. The high value for March in the South Georgia curve reflects the high percentage frequency of o z z < bJ z UJ O a. 3 1- < UJ 10 -2. J F MONTHS Text-fig. 51. Above: A, estimated frequency of weaning; B, monthly incidence of lactating females in South Georgia catches, and C, in pelagic catches. Below: average monthly sea surface temperatures in South Georgia waters and on the pelagic whaling grounds. lactating females in the sample for this month (Text-fig. 50); it may well be too high. Even so the slope of the descending limb of the South Georgia curve is fairly close to that of the expected curve. In explanation of these results, it is suggested that the southward migration of females with suckling calves is dependent on, and limited by, seasonal changes in the temperature of the sea. In latitudes from 560 S. to 66° S. the average sea surface temperature is at a maximum in February (Mackintosh, 1946, fig. 11), when it is 1-20 C. higher than in December or earlier. The average surface temperature for March is also much higher than the December value and somewhat higher than the January surface temperature. Also, the summer rise in the surface temperatur
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