THE DEVELOPMENT AND LIFE-HISTORY OF KRILL 



Table 14. Adolescent lengths : from Fraser's report 



123 



NB. Measurements approximate to nearest whole number. 

 Table 15. Analysis of the adult female catch per month from later commissions (rough analysis) 



Eraser has established that growth from the egg to the ist adolescent stage occupies approximately 

 7-9 months. On this basis, if the eggs are most often met with in February, March and April, the 

 maximum occurrence of stage 1 should be in October, November and December. It is significant 

 that these are just the months when this maximum is encountered, with an extension into January 

 in the case of the males, and into March in the case of the slower growing females (Table 13 A and B). 



The rest of the period of growth from stage 1 to maturity occupies another 12-16 months in the 

 males and 12-18 in the females. Ruud showed that the life cycle of E. superba occupied at least two 

 years. He drew attention to the two classes of kriU recognized by the whalers as "blue whale" and 

 "fin whale " kriU respectively, and diagnosed them as representing the two age groups, adolescent and 

 adult. But owing to lack of material, and not having devised a method of gauging the stage of develop- 

 ment of the adolescent males and females, the growth curve which he figures is too steep, and does 

 not give an accurate idea of the growth rate throughout the whole of the growth period. 



Ruud suggested that after pairing and spawning the adults died off. I think this is very likely, for 

 although at the end of April I found females, which had spawned and were feeding actively (a thing 

 they are unable to do while gravid), no fully adult females or males were found between May and 

 October. This may of course be due to lack of material, which in all commissions of the R.R.S. 



