PLANKTON 177 



the frigate bird which is also of tropical habits, is seldom found farther south than 

 Talara in the cool water of the Peru Current. 



Squids were widely scattered and they varied in size from forms measuring a few 

 centimetres to others reaching a metre or more in length. A squid which is referred to 

 Omastrephes gigas by Wilhelm (1930), but which, as far as can be judged^ from photo- 

 graphs, appears to be Dosidicus gigas (Orbigny), was met in great numbers washed up 

 in the harbour of Talcahuano. We are informed by Dr Ottmar Wilhelm that this 

 phenomenon may be a serious problem to the harbour authorities, not only because 

 the floating bodies are so numerous that they choke the harbour and interfere with 

 shipping, but also because of the disagreeable consequences of their decomposition. 

 The cause of these cataclysms, which in their effects resemble those of El Nino off 

 the Peruvian coast, is as yet unknown. They are described in more detail on p. 233. 



ZOOPLANKTON 



Light upon the distribution of the larger animals seems to have been thrown by the 

 catches of zooplankton. The mass of plankton has been consistently large, but the average 

 volume per net was slightly larger in the lower latitudes off Peru than in the Chilean 

 latitudes, as is shown in Table X. The contrast is greater if Euphausians are considered 

 by themselves. Off Chile, catches of Euphausians were more frequent; they were con- 

 sistently larger and their bulk occupied a very much larger proportion of the total 

 plankton catch. Off north and central Peru, on the other hand, the plankton had a small 

 Euphausian element, but the total bulk was otherwise greater. The krill and the whales 

 seem to be correlated off Chile ; the guano industry, anchovy and heavier plankton, off 

 Peru. Krill is of course the staple of whale food in the Antarctic: off Corral, whales 

 have been taken with Eiiphausia vallentini in their stomachs, but whether in these 

 latitudes they feed in the proper sense as they do in the Antarctic is doubtful. With rich 

 plankton off Peru, we find the enormously heavy shoals of anchovy, and upon them the 

 birds, seals, dolphins, bonito and other animals are said to subsist. 



Table X. Relative abundance of Euphausiacea and of other animal plankton off Chile 

 and Peru as shown by the volume of settled organisms 



* These figures include only samples in which the volume of Euphausiacea exceeds 200 c.c. 

 1 I am indebted to Mr G. C. Robson for this suggestion. 



