SUMMARY 239 



Grounds are adduced for identifying the colours of very unusual appearance met with 

 off Pisco, Callao and the Guafiape Islands (Plate XVI, figs. 6, 7 and 11) with the agiiaje 

 phenomenon rather than with the appearance at the surface of normal animal plankton 

 (pp. 222 and 229 33). 



AGUAJE 



A condition of the surface water in which discoloration, fish mortality and liberation 

 of hydrogen sulphide take a leading part, is known as agtiaje. Compared with other 

 records, our results support the view that aguaje may result in coastal water from a 

 sudden rise in temperature. Under the apparently normal conditions of the present 

 survey, it was found to coincide with the northern anticyclonic swirl at those points 

 where its oceanic limb, the warm wedge, was converging with the coast. It appears also 

 to be brought on by convergence of the abnormal counter-current known as El Nino. 

 Aguaje, although an abnormal phenomenon in the sense that it may upset the balance of 

 nature, is therefore liable to occur in either normal or abnormal conditions (pp. 229-33). 

 The nature of aguaje is summarized : its effects are shown to vary from the mild met with 

 in 1 93 1, to the extremes which kill plankton and fish, cause the guano birds to migrate, 

 and produce the "Callao Painter". 



MORTALITY OF SQUIDS ON THE CHILEAN COAST 



Large quantities believed to be Dosidicus gigas (Orbigny) were found washed up in 

 Talcahuano harbour, but no connection could be found between them and the abnormal 

 phenomena noted on the Peruvian coast (p. 233). 



BOUNDARY OF THE PERU COASTAL CURRENT 

 Coastal and oceanic conditions contrasted 



Results summarized in foregoing paragraphs have shown the more important bio- 

 logical and hydrological characteristics of the coastal current to be attributable to up- 

 welling of lower layers and their mixture with surface water masses. Equivalent 

 characteristics of the open ocean are contrasted in Table XXII. 



The distribution of surface isotherms seems the most comprehensive characteristic, 

 for isotherms usually run east and west parallel to latitude, but they change direction 

 under the preponderating influence of upwelled water and run parallel to the coast. 

 If their change of direction is taken as the western boundary, the whole area surveyed 

 by the ' William Scoresby ' lies within the Peru Coastal Current (Figs. 16 and 17). An 

 arbitrary boundary is suggested on the basis of Schott and Schu's chart of mean annual 

 isotherms (Fig. 68). 



Northern boundary and the Equatorial Counter-current 

 The northern boundary is shown to be easily recognizable as the convergence of 

 cool upwelled water of moderate salinity (> 2S'°'^°loo) with the warm poorly saline 



