REACTION OF KRILL TO SHIP AND NETS 



261 



Table 52. Varying turbulence of the sea and its itifluence on the catches of the oblique {100-0 m.) stramin 

 nets. Night-time data in roman type, daytime data in italics 



keeping them from fouling the warp as they entered the water. In heavy weather however, to safe- 

 guard life, this practice was abandoned and we towed head on to wind and sea. In other words we 

 were hove to, the vessel plunging violently as the stern rose and fell, 20, 30 feet or more, in the cfests 

 and troughs of the waves. The sudden downward movement of the hull would give the nets a sharp 

 backward thrust and it was probably this more than anything else that led to the spilling of the catch. 

 An interesting general inference that may be drawn from Table 52 is that with every developmental 

 phase of the population it portrays it provides substantial support for our evidence that the main 

 concentrations of these animals are never very far away from the surface. For if it were not so and 

 such concentrations had a much wider bathymetric range, extending downwards into the tranquil 

 water below the relatively narrow zone of surface turbulence, then the influence of the state of the sea 

 on the catches of the upper oblique nets would not, either by day or by night, be nearly so pronounced 

 as it transpires to be. 



Activity and vigour of the krill themselves 



As might be expected, the measure of evasion achieved is greater in the older and more vigorous 

 animals than in the younger and weaker, presumably because the latter, although they may be able 

 to see just as well as the adults, are unable to dodge away so rapidly or so far. The mounting capacity 

 to evade developed by the krill as they grow is illustrated in Table 53 in which the three broadly 

 grouped developmental phases portrayed may be described in general terms as follows: the under 

 16 mm. group, vast majority early and late surface larvae with some very early adolescents; the 

 16-20 mm. group, vast majority early adolescents; the over 20 mm. group, older adolescents and 



